Andrew Prestridge | July 21, 2022
Andrew Prestridge | July 21, 2022
Gears come in a wide variety of shapes and sizes, many of which look awfully similar. The difference might not look like a lot, but gears of different pitches (or modules) will not run on each other! The same goes for gears of different pressure angle (although at a small pitch, you might get away with it for a little while). To help solve this identification crisis, we've created a chart of gear tooth profiles.
The gear identification chart is designed to help you identify an unknown gear, even if only a few teeth remain intact. The chart has templates for:
We've created a downloadable gear template to identify the pitch, module, and pressure angle of your gears
The chart includes true-to-scale copies of all the common pitch and module sizes in both 14.5º and 20º pressure angles.
Note: while the preview image is not to scale, the downloadable PDF certainly is!
A gear gauge has the gear tooth profile for one or more gears. By comparing the known gauge to an unknown gear, you can determine the gear's pitch (or module) and pressure angle. Some gear pitch gauges are metal and can run against a gear, while some are paper and allow for visual comparison.
We've made a video where we walk through our steps for identifying an unknown gear. One of the simplest, and sometimes most impactful tips is in counting the teeth on the gear. Use a Sharpie to mark each tooth with a dot as you count it, and then mark every 10th tooth with a dash. This simple move helps keep the count on-track and avoids skipping or double-counting.
Counting teeth isn't hard, but in a well-made gear all teeth should look nearly indentical. Combined with a high tooth count, or small module (tiny gears), it gets easy to miscount and end up making or buying the wrong gear.
Once you know what your gear is (tooth count, pitch/module, and pressure angle) you have all the information required to make a replacement gear. Fortunately, involute gear cutters have the tooth geometry in the actual cutter, so you don't need to worry about the complex curvature – just getting the right cutter.
We supply a wide variety of involute milling cutters for both Diametral Pitch and Module gears in both 14.5º and 20º pressure angles. We recommend checking out our gear cutter database to find precisely the cutter you need to make your replacement gear (or any gear you need!)
Templates are provided for both metric (Module) and imperial (Diametral Pitch) gears
14.5º and 20º are the most common pressure angles for nearly every modern gear
The reference chart includes the most common equation for reverse engineering gears
Andrew Prestridge | March 8, 2022
The involute gear cutter chart is designed to help you select the correct gear cutter based on the specifications of the gear you're trying to make. In short:
We've created a free involute gear cutter chart to select the right tooth count based on cutter number
The chart includes: tooth ranges for module cutters, tooth ranges for diametral pitch cutters, and even the tooth ranges for expanded "half-size" cutters
Involute gear cutters are a great option when you're looking to make a small number of gears or a replacement gear for one that's broken. Gear cutters work great in mills, and often times allow you to expand the capabilities of machines you already own.
To use an involute gear cutter effectively, you need to know the pitch (or module), pressure angle, and number of teeth of the gear you're trying to make. The cutter will be specific to the pitch and pressure angle, so they need to match exactly. Each gear cutter is also only suitable for cutting a range of tooth counts, and it takes eight different cutters to make every gear from 12 teeth to a rack ("infinite" teeth).
The numbering system is reversed between diametral pitch and module, so we recommend checking out our involute gear cutter chart to make sure your cutter will mill the gear you need.
While you need the right gear cutter to cut the gear you want, it's just as important to be able to hold onto the cutter. A typical gear cutter has a circular bore through its center, with a keyway. This lets the cutter run on a standard arbor in the spindle of your machine.
The other, typically less important, dimensions are the width and outer diameter (sometimes called "cutter diameter"). While literature provides a good reference, we recommend measuring these directly on the cutter you're looking to use to ensure the best quality gear.
Each cutter will only cut a specific pitch (module) and pressure angle
Each cutter can only cut gears within a narrow range of tooth counts
We made a chart to compare cutter number and tooth range for metric (module) and imperial (pitch) gears cutters
If you have a question and need help finding a cutter, whether it is in our store or not, please send us an e-mail to;
Andrew Prestridge | January 26, 2022
Nearly every shaft diameter has a corresponding standard keyway width and depth. While a designer is free to specify any keyway they wish, straying from the standard option is likely to increase the cost, time, and complexity of the part. Many keyways are milled directly into a shaft or broached into the corresponding bored holes. Changing the width and depth of a milled keyway is straightforward, but much less so when broaching.
Standard keyway dimensions
We built a calculator to determine the standard keyway based on your shaft diameter, either in inches or millimeters.
There's always the option of increasing the width of the keyway beyond the width of the end mill. In theory, a small end mill is capable of cutting every keyway larger than itself. However, this quickly becomes costly and inefficient as the smaller cutter will take longer and be more liable to breaking than an appropriately sized alternative.
While a small end mill can cut any keyway into the outer diameter of a shaft, the story gets more complicated when one considers the mating surface: a keyway on the inner diameter of a bore. These keyways are often cut via broaching, which uses a specialized cutter that passes through the bore and takes incremental cuts along its path. These small cuts are typically the width of the cutter and gradually get deeper into the base material. While a broach could be ground down to reduce its width, the process is both time-consuming and permanently alters the tool. And special tooling comes with a special price. There are two other ways to make ID keyway slots, using a shaper and EDM.
Caption for above graphic
The depth of a keyway can be more forgiving, both on the shaft and inside the bore. Increasing the depth of a milling cutter is a trivial exercise, and multiple steps can hone in directly to the required depth. The depth of a broached keyway is moderately more challenging, and will typically involve the use of shims to shift the broach further from the center of the bore. The broaching process may involve multiple passes to avoid cutting to final depth all at once. Cutting too deeply can:
Shimming becomes increasingly common as the depth and width of the keyway increase. Intuitively, this makes sense since the greater the removed material, the more difficult it will be. Custom shims are also much easier to manufacture (or improvise) than a custom broach or a custom bushing.
Bushings, which are to guide the broach through its cut, are often only available in the standard sizes. Depending on the size of the bore, only a couple (and often only one) bushing will be available. The lack of bushings determines which broaches can be used, and what keyway width is achievable.
Custom bushing for non-standard broaching. Welding rods make for quick shims in a pinch
All of this complexity: elaborate milling routines, grinding broaches to fit, and fabricating custom bushings and shims, can be avoided by simply choosing the standard keyway for ones shaft. Of course, the standards are different depending on whether you’re working in inch or metric units, but two competing standards are still better than the alternative.
Width and depth are easily changed by choosing endmills of different sizes or taking multiple cuts
Broaches can be ground down to decrease the width of the keyway
Adding additional shims can increase the depth of a broached cut
These alternate process work well, but may not be in your machine shop
Andrew Prestridge | December 18, 2020
If your chuck is stuck open or closed, isn't running true, or feels sticky or crunchy it's a good time to take apart your drill chuck. It may be broken and you need to fix your Jacobs Chuck, or it’s starting to wear and you don’t want it to get worse, or everything is working fine and you want to keep it that way. Another good time is when you first buy it and you want to put it in tip-top shape before using it heavily, or maybe you’re curious and want to see how it works. Fortunately, the original design is both effective and easy to rebuild with the right tools. For that reason, it hasn’t changed much since it was introduced in 1902.
Dirty Jacobs Super Chuck receiving some much needed attention
Most problems with your Jacobs Chuck can be solved with a good clean and lubrication. For more complicated issues, repair kits offer replacements for all the components in the Jacobs Chuck. The process to remove the sleeve is the same for both, and we found it takes about 10 minutes with our helpful Service Ring. Replacing parts, cleaning and lubrication may take longer.
A service ring, dental pick, and some WD-40 goes a long way to revitalizing your chuck
Here's a basic guide on removing and repairing your Jacobs Chuck. Check out the whole process in our YouTube video Rebuild a Jacobs 14N Super Chuck
Check out our video on repairing a Jacobs Super Chuck here:
Maintenance is straightforward and quick to complete with a Service Ring
The design has remained relatively constant since first introduced in 1902
With a touch of grease and a quick clean your chuck can last for generations
Andrew Prestridge | September 4, 2020
Our World is Impressive – it gives us instantaneous information through the Internet and this connects us for better or worse. But how about connecting across languages?
During our research of historical resources regarding mechanical devices, we get stuck trying to figure out how to locate (and then process) reliable information in languages other than English. Based on global statistics if we only search English sources we are only researching what the minority of the global population knows.
In our exploration of early gears and mechanisms, we hit a large roadblock when trying to research Ancient China. The South Pointing Chariot (a purported Chinese navigational aid), was one of the earliest geared mechanisms found in references, and so China seemed like a logical first step. But we were quickly reduced to looking at photos and drawings since we could not translate the text. Short of learning Chinese ourselves, we clearly needed help with translation to unlock the long history of a rich technical culture.
Rendering of the South Pointing Chariot
Luckily, we found that Joseph Needham (1900-1995) had dedicated his life to documenting Science and Civilisation in China. His story is unique and the interested reader would benefit from learning about him and his large volume of work, which spans countless topics. One of the many volumes he produced covered mechanisms including gears. Needham could not substantiate the South Pointing Chariot, but did document very early uses of gears. [1]
Relics of ancient Chinese gears
Geared mechanisms require a drawing to communicate their distinctive properties, and this at least gives us a technical language that can transcend spoken and written languages. These photos alone are enough to start a lively conversation amongst those of us that marvel over the mechanical need of their makers. Math and good technical drawings are universal. Today we can communicate technical knowledge sometimes better than other types of information.
Voyager 1 is the farthest man-made object from earth in interstellar space. As it travels across the cosmos, Voyager carries sounds and images from Earth encoded onto a golden record, their interpretation does not rely on any discoverer's understanding instructions written in an Earth-based language.
Voyager 1 Golden Record. (Image credit: NASA)
Instead, playback instructions are given in a drawing using scientific principles that are universally true: the hydrogen atom and its characteristics, binary counting, and a waveform. In the absence of any text or language it’s expected that these technical principles give the best chance of universal understanding.
As Voyager looks out to space and the future, we reflect on the past of our own planet. Could an ancient gear serve as a previous-day Voyager of technological advancement, and if so, why have we not found more ancient gears? Unlike the lone spacecraft, sheltered from all but radiation, terrestrial gears must survive the elements, corrosion, and interference from future humans.
Artist illustration of the Voyager 1 Space Probe (Image credit: NASA)
Ancient gear materials were expensive - and a broken or worn gear was likely melted and re-used. Steels corrode over time so an archeological dig finds slightly reddish soil where an artifact had oxidized and disappeared. Only in the rare case is an artifact removed from the temptation for repurposing and sufficiently sheltered to be preserved through the centuries.
From an Ancient Shipwreck the 2000-year-old Anitkythera Mechanism was found in 150 feet of cold seawater. Despite its corrosion, this lone example continues to amaze us today as it shows an advanced understanding of astronomy, horology, mathematics, mechanical elements, metallurgy and especially the use of triangular tooth gears. This was decidedly not the first mechanism made by the maker. Clocks tens, hundreds and thousands of years later continue to use triangular tooth gears.
As we speculate about various undiscovered ancient inventions scattered across the planet, so too may discoveries lie hidden in untranslated texts. And yet, even if we cannot translate every language and access every library that ever existed, we can be certain of the language of the trades with their underlying true science and use of the universal. Personally I’d prefer fully understanding an artifact or drawing to find the clever bit.
The history of mechanical devices is astonishingly long, here is our timeline.
-VH
Spoken and written languages were the earliest forms of communication
Recovering relics gives glimpses of actual technical advancements, but are often puzzles to decipher
As we look to communicate out into space, we rely on scientific phenomena to convey our message
Andrew Prestridge | September 4, 2020
...stands on the shoulders of the ancient navigators, locksmiths, clockmakers, and millwrights. While many of their relics and inventions have survived the test of time, many more are probably lost. Humans have been extremely clever for thousands of years, most of which predates our modern ability to write, record, document, photograph, and patent.
These early innovators did their work to solve problems, improve their lives, fully utilize their capabilities - and just because they could. We know these traits exist today, in people that are more sharing and more open than ever in our connected world. We've done our best to research and compile a long history of gears and mechanical systems kept up to date
Rendition of what the South-Pointing Chariot may have looked like. Science Museum of London.
The Chinese claim to have had gears mentioned in their archives as far back as 5,000 years ago, but no relic exists to prove the claim; it stands only as a legend. The ancient geared device was a South Pointing Chariot – a device to aid in navigation. The instrument always pointed South by connecting to the wheels of a chariot through a differential geartrain
Eratosthenes and Archimedes were making instruments and documenting their work around 250BC. One such celestial calculator was the Antikythera Mechanism, which shows stunning craftsmanship, ability, and knowledge to predict eclipses decades in advance.
Most certainly this device was a close secret to kings and rulers, but the concepts and skill must have taken generations to develop. The name of the maker, or makers, remains unknown. The model of the heavens is expressed in a complex gear train. The relic is a great example of undocumented technology that is far more advanced from anything in the recorded history of that time.
Antikythera Mechanism – how it actually looks after recovery from a shipwreck
The Silk Road allowed trade and ideas to spread and travel long distances. Along with silk, technology and ideas could and did spread long distances.
The next time period from 200BC to 1500AD showed more widespread use of clocks, mills, water pumps and mechanisms with increasing complexity of gears and gear types. Da Vinci left drawings of many mechanisms and pushed the arts forward. Christopher Columbus navigated to North America by 1492. The quest for sea trade, and safer navigation, put instrument makers and astronomers front and center from 1500AD to 1773AD. This culminated in the Harrison clocks and the marine chronometer, and humanity’s first ability to reliably determine longitude.
The United States was new in 1776 and the Industrial Revolution moved small gears from clocks into mills, steam engines and many new machines. Textiles played an important part in the expansion with looms and sewing machines. Key names in the period up to 1900 include Henry Maudslay, Joseph Whitworth, Christian Schiele, William Gleason, George Grant, Edwin Fellows, Herman Pfauter, and Max Maag. In their quest to perfect gear types and the machines to make them, these were the namesakes of numerous companies and countless pieces of equipment still in operation today. As technology improved, the prime movers changed from water and wind to steam, diesel, and the internal combustion engines. By 1901 more gears than ever were needed to keep up with the demand from Henry Ford and the dawning automotive industry.
Gears in mesh, in a machine to make gears
Although gears are everywhere, their place in machinery is almost always buried deep within a gearbox – out of sight. Whether slow or fast, open gearing is hazardous near humans. So even if they do not require a gearbox, industrial gears are usually shrouded behind covers and enclosures. But while they may not always be visible, we have all benefitted by the life gears have enabled.
Follow along as the Gears & Grounds newsletter rediscovers the history and manufacture of all types of gears. The last chapter in gearing is not complete and there is plenty of room for innovation as our understanding, manufacturing, and applications of gears continues to grow and improve.
Know more, do more.
VH
Andrew Prestridge | September 17, 2020
Few professional books are as ubiquitous as the Machinery’s Handbook. This book can rightly be called a machinist’s bible, and not just for its super thin pages. Clocking in at nearly 3000 pages, the 31st edition Machinery’s Handbook adorns a special corner of my desk, always within arm’s reach.
The shear body of knowledge and content span multiple lifetimes of careers in machine shops (the first draft was published in 1914!), and the index for each logical section is many pages long. The Digital Edition companion is increasingly useful too.
The latest edition of the Machinery's Handbook, with corresponding Digital Edition
What sets the Machinery’s Handbook apart (it’s often called the Machinist’s Handbook, which somehow seems more appropriate since the machinist is the one who owns the handbook, but is nevertheless incorrect) is not just its sheer breadth, but also innate practicality.
Across thousands of topics it provides enough information to gain an understanding and then go out to the shop and deliver. Just as DNA is considered the "recipe for life" the Handbook is the DNA of our modern, mechanical world.
Key to this claim is that the reader learns enough from the single book that he doesn’t need to consult additional references. Far too often a book will lightly touch a topic, offering a general familiarity, but not enough information to actually do anything. Or, a dense reference material might dive deep into the weeds, offering complexity that takes a degree in mathematics to unravel. Striking a delicate and precise balance, the Machinery’s Handbook delivers just enough information to know what to do.
The Handbook contains countless charts, formulas, and definitions
Perhaps equally interesting is how the Handbook has remained relevant in our time of modern connectivity. The importance of the physical book is obvious for the machine shops of yore, without access to the Internet from every phone, tablet, or toaster. And yet, it has remained important by offering a reputable compilation of crucial information.
Some of the Handbook’s content is also available in digital format, but most shops trust the physical book that has developed over its 106-year history. In a way, countless machinists are staking their reputations on the accuracy of the Handbook.
Customers demand correct parts, and a machine shop can only deliver these when they have correct information. When weighing the cost of scrapped parts and disappointed customers, the cost of the Handbook pales in comparison.
The first draft was published in 1914, and has been consistently revised and improved over 31 editions
The hardcopy of the 31st Edition has over 3000 pages of formulas, charts, and definitions
Almost every conceivable mechanical discipline is featured, with enough specificity to solve real problems
Andrew Prestridge | October 1, 2020
Galling is caused by the asperities (high points) of one component puncturing the protective oxide layer of another, and then transferring material between the two. Stainless steel and Inconel have impressive corrosion resistance, but come with one critical drawback: galling.
Example of galling on a stainless steel fastener
The Gauls in Rome, Alphonese de Neuville. No relation to galling. [1]
However, under the “right” (or “wrong,” galling is usually bad) set of conditions this oxide layer can be punctured and leave the underlying material exposed and likely to transfer. All materials have an inherent roughness, and threaded fasteners (nuts and bolts) are no exception.
If you're looking for some more information on thread pitch, check out our article on Pitch and its Relation to Screws and Gears and for a helpful guide.
When screwed in, these threads are in close, high-pressure contact - any imperfection or roughness on one piece may act like a shovel, and break through the oxide layer on the opposite piece. The freshly exposed material is dug out to the surface and often creates a new high point on either the original piece or it gets transferred to the other piece and becomes a high point there.
This new high point continues the digging action and accelerates the material transfer. In this process, the exposed material is in close contact before an oxide layer can form, which allows it to cold-weld from one part to the other.
Stainless steel fitting showing signs of severe galling from over-tightening. [2]
Cold-welding can bind two pieces together as one, and cause them to seize up and ruin the threads. The unavoidable roughness and high-pressure environment of a threaded fitting may make galling seem inevitable, but all is not lost!
Galling resistance chart for different materials
Galling occurs when high-pressure contact transfers material between two bodies, like nuts and bolts
Go slow, use thread lubricant, and pick smooth threads with a coarse pitch
Using materials of different hardnesses – one hard, one soft – goes a long way to preventing galling
Andrew Prestridge | September 8, 2020
If you mesh two gears together and rotate one - whether it's a spur gear, helical gear, or any other kind of gear - the two contacting surfaces will roll off each other, not slide. The difference may seem semantic, just a choice of words with no real consequence, but it's important to consider this all the way from gear design to gear production. This difference has a huge impact on the life and performance of the gear, and it all comes down to friction.
Animation of two gears rolling off each other in mesh [1]
When one surface slides against another, like a pencil across a piece of paper, a tiny amount of material is worn off and transferred from one surface to the other. While this is all part of the design for a pencil, so the graphite is transferred to the page and marks are visible, it’s not so desirable for gears.
Gears need to work for many millions of revolutions and can’t be resharpened like a pencil. So how do gears work? Gear teeth are specifically designed with an involute profile shape so that they don’t slip or slide across each other, but roll.
Progression of gears rolling
To help visualize the difference we can imagine a basketball rolling along a flat pavement. If we think of one bump on the basketball and its journey through a single rotation, we see that it starts at the top of the ball, comes down, comes in contact with the ground, then goes back to the top, and repeats the cycle. If we could zoom in to the exact point where the bump on the ball meets the ground we’d see that each spot is only in contact with the ground for one instant.
As soon as the bump is at the very bottom, it’s already started heading up and away; the bump never has time to slide or drag along the surface. In the real world the ball is not a perfect sphere, and the ground is not a perfectly flat plate, but the underlying physics still stand (there are also intermolecular forces that attract and repel the two objects but we don’t need to talk about that yet).
Arrows show the direction and velocity of each point on a circle as it rotates on the ground [2]
Gears behave the same way, as soon as the gear teeth mesh and one gear comes in contact with the other, those points become almost synced together and both move at the same time. The points don’t slip or drag, but rather come together then come part, like the bump on a basketball or someone tapping a pencil instead of drawing a line. As a result, the gears have a smooth, continuous motion that minimizes wear.
Each point on one gear engages and disengages with the other gear without relative sliding
This unique and universal attribute has only been made possible through the clever utilization of the involute profile, also called the evolvent, in the gear teeth. This profile, formed by wrapping an imaginary string around a circle and “unwinding” while holding taut, has been investigated since Girolamo Cardano in 1545 and Christiaan Huygens in 1656. A proper mathematical derivation of the involute took another 120 years and the interest of Swiss mathematician Leonhard Euler in 1781. [3] Anymore, except for clocks, nearly every gear in existence uses the involute profile.
If you want to transmit power, the involute is the only way to roll.
Rolling reduces friction and wear between a pair of gears in mesh
Points of contact come together and come apart, but do not slide relative to each other
The involute profile, an "unwound circle," forms the tooth shape of most modern gears
References:
[1] Rocchini, Claudio. Involute Wheel. Retrieved from Wikimedia: https://commons.wikimedia.org/wiki/File:Involute_wheel.gif
[2] Algarabia, Rodadura. Retrieved from Wikimedia, https://commons.wikimedia.org/wiki/File:Moglfm2207_rodadura.jpg
[3] Radzevich, Stephen P. Gear Cutting Tools: Fundamentals of Design and Computation. Taylor & Francis Inc. ISBN: 9781439819678
Andrew Prestridge | November 1, 2020
An idea has to start somewhere and when you get a good one, you need to catch and share it.
Many new ideas for physical products end up as a Patent. Others ideas may come under the protection of a Copyright. Some end up as a proprietary secret and exist as a line of code or subroutine or algorithm. The first time a consumer may experience the ideas of the inventor may be years or decades after the actual act of creation. But that is the ending of the story, and honestly by this time the wonder and fun of invention has passed.
Let's get closer to the point of origin, but let's also talk about how ideas have been made throughout history. Remember us humans have been here on this earth for a very long time (millions of years) having ideas. The way we keep these ideas and share them with others has changed a lot. In the earliest times the idea may have been communicated by simply pointing, drawing in the sand, or later through language. History is replete with us losing technology for a century or so - maybe longer only to regain the idea. Growth and accumulation of ideas is anything but linear or continuous.
The Mesopotamians are credited with one of the first written languages dating back as far as 3500 BC. They wrote on clay tablets using Pictograms and then Cuneiform. These tablets were widely available and depending on how they were stored, fairly durable. If you want to know more about these beautifully decorated tablets that are full of marvelous things, get to know Irving Finkel, curator at the British Museum by watching his YouTube Video. If you click his link and get lost at Irving's Museum - this article was still worth writing as I think he is one interesting, intelligent and colorful character. Irving, if you make it to Ventura CA, lunch is on me.
Ancient Cuneiform tablet, 3100-3000 BC
The Chinese as early as 200 BC were thought to have invented paper. Expensive and tightly held by Imperial Rulers, it was not generally available. It took until maybe 1200 AD before one could get a piece of paper for less than a few days wages (surmising). This fact alone makes one wonder how many good ideas were held in other ephemeral ways only to be lost (bark, banana leaves etc). Paper is important to the story as, in my opinion, it is still the most likely medium to capture the idea of the day.
The concept of owning the rights to ideas is relatively modern. Most point to the Venetian (Italian) patent office in 1450 AD as being the first. By the way, the first Venetian patent was for a lifting barge that could lift and transport marble - countertops anyone! Others reach further into History and point to the Greeks who effectively had patents for cooking recipes around 500 BC. Regardless, the Italians really primed the world for a flood of new ideas that could be owned and accumulated. The US patent office did not open its doors until 1790. The only way to submit a patent to these early Patent offices was on paper.
Venetian Patent Statute, 1474
The most incredibly pleasing, highly experiential, and expressive way to capture and communicate any idea is to get a piece of paper and draw the object or concept - probably accompanied by writing a few sentences or measurements. It is under-rated, under-taught at schools, and if you don't get it - you need to keep reading. If you have not broken it down into its parts, they are all pretty incredible and here they are...
First you must charge your brain with enough general knowledge so that you can build with it (does not require a school, but it sometimes helps). This also presumes you know a language and can use it to communicate. It also presumes you can draw objects in a way that is universally understandable. Packing the brain with good fundamental knowledge may take a while. You also need to be aware of your surroundings and have a variety of experiences to use as building blocks.
By hand. Yes, beginning with any of the three above. Writing with our alphabet and number systems to clearly communicate ideas, drafting complex objects to express geometry of physical objects, and doing both of the former with artful expressiveness. Seems simple but how many years does this take to develop, 10, 20, 30 or more years?
Student drafting and sketching an architectural model
Practice, Coordination, Dexterity. Our bodies are just flat-out amazing. The other most often heard phrase is Eye - Hand Coordination. And there is more in this area than I will ever know, so let's leave the details alone for others more qualified to explain, but keep the wonder.
Plain old copy paper will do. It is everywhere, cheap and pretty consistent. Most of the copy paper you find is designed to receive ink from some sort of printer. But if you start to write and draw more frequently, some heavier weight paper is usually in order. The details are interesting and endless. But once you find your chosen paper you will know. The indentations left by either Pen or Pencil can end up being another expressive element to your drawing when cleverly used and they are very dependent on the paper you choose. Today we have the choice of some very good long-lasting paper described as 'archival' or 'museum quality'.
Really graphite, but commonly misnamed Lead or Leads. Writing and drawing with a pencil can be extremely expressive. Combine different hardness's to make thick and thin lines, lay the pencil on the side to create shading. Erase, smudge, draw with several different pencils. For me, the greatest pencil on earth is the U.S.A. General's Cedar Pointe #333-2HB made by the General Pencil Company. Writing a small new idea with so much history in your hand-well that's just awesome.
USA General's Cedar Pointe #333-2HB
Black ink is very corporate, Blue is a close second. But there are many more color options out there so go for it. The methods working where the pen meets the paper are usually, ball-point, fountain, rollerball, felt-tip, gel, and a few others. Ball-point is easy and a good starting point. A fountain pen has been my serious drawing preference when drafts come down to making the final drawing.
Ink needs to be married to the paper along with the skill to make it work. Inks are more difficult for this reason, so plan on some extra time to get proficient. Technical drafting was an early job, and at that time the Keuffel and Esser Company made the best technical ink pens. Various widths, stencils and lettering guides gave freedom and structure to the draftsman simultaneously.
Keuffel and Esser lettering guides for drafting
Skip all the known fonts, throw away the computer, your own hand-written font is better. It will be unique and impossible to copy. Everyone will know your hand made the mark. It somehow results from the miraculous pathway from formation in your brain, through your body and onto the paper. Typing this article is getting the idea to you, certainly most of use use computers daily. But I proclaim that we are missing an element of communication. Practice recording your ideas by hand, find your unique font, and start to communicate at a higher level.
To have an idea, you must have some reason for the use - "necessity is the mother of invention" some say. But this means there are many ideas already understood by the tribe and are in use, all inferior to the new one. Whether you're making a list for the day or drawing a new product targeting tennis for older players, it all starts at the same place. Newsflash- there is no end to new and very good ideas. Maybe the idea is just your list for the day - a memory device. Or it could be the idea that will help your current project along the track, or change the course of your life and maybe others too.
Whether you're writing in paper, clay, or canvas, find a medium to record your ideas
A good pencil is an extension of your hand, and with it ideas can flow more gracefully
The control and finesse of an ink pen adds elegance and a finished appearance to a final document
Andrew Prestridge | October 5, 2020
We’re all familiar with the fact that diesel fuel goes into diesel engines - but truthfully when Rudolf Diesel patented the original Diesel Engine concept in 1895, it had the universal claim the engine could burn, “any kind of fuel, whether solid, liquid, or gas.” And furthermore, the invention and perfection of diesel fuel came much later. Over a century later - diesel fuel is the most common fuel used today, but how did we get here?
Portrait of Rudolf Diesel c. 1900
Rudolf Diesel was born in March of 1858 in France to Bavarian immigrants. He excelled academically and was taught by Carl von Linde the noted German Scientist famous for the invention of refrigeration. Diesel learned about the theoretical Carnot cycle from Linde, which is the thermodynamic cycle representing the perfect conversion (no entropy) of heat into work. The Carnot cycle can also be used to analyze refrigeration cycles.
Pressure and Volume in a theoretical Carnot Cycle
Chasing the Carnot efficiency ideal in the construction of a new engine design became the guiding light for Rudolf - The technical concept and research basically set the bar, he just needed to make the most efficient engine possible. The results are the modern diesel engine we know today.
Mechanically, Diesel started by studying steam engines, powered by coal, and was able to compare their low efficiency to the Carnot cycle. He then moved to the newer internal combustion engines, powered by gasoline, which still struck him as inefficient. The drive for the highest possible fuel efficiency led Diesel in a unique direction. Strong castings were required to achieve the combustion pressures for the diesel engine, a hard earned lesson that left Diesel injured on several occasions due to explosions. The difficult problems became clear, the system to inject and distribute the different types of fuel at the correct time and duration during the combustion cycle.
In early 1890 he had a chance to follow his personal aspirations to make an efficient engine and by 1893 he had filed the first German patent: DRP 67207. This mechanical work on the diesel engine was done in Germany at the MAN company headquarters in Augsburg Germany.
Long stroke diesel engine prototype, from Diesel's first US patent
His first US patent titled "Method of and Apparatus for converting heat into work" (US 542,846 July 1895) very clearly describes how the diesel engine works and relates it back to a Pressure-Volume(PV) chart. The diesel chart is crafted in the same manner for the Carnot cycle. The patent also shows the iconic diagram of a very long stroke diesel engine prototype
While "Diesel fuel" is synonymous with "diesel engines," when Rudolf Diesel was first inventing his engine he had envisioned a wide variety of potential fuel options. In 1895 the main options available were:
Olive Oil or Peanut Oil are common oils still in use today (more often for cooking than burning), they contain saturated and unsaturated fats. Because many vegetable oils become rancid, they are not commonly found in industrial uses (unless further refinement is made). Recently vegetable oils have been recycled from restaurant fat-frier's and used as biofuel in diesel engines. This type of fuel oil was definitely available and could have been a fuel choice, but it is not mentioned in either patent.
Whale Oils were used for Illumination prior to the widespread use of kerosene. This type of fuel oil was less likely to be a choice, and also was not mentioned in either patent.
Formed from ancient Phytoplankton (plant) and Zooplankton (animal) these marine life forms rain their organic matter onto the seafloor. The formation of Mineral Oil takes many millions of years undergoing increased heat and pressure from geologic processes as the layers of organic matter transform to Mineral Oil and migrate into traps.
In 1856, the Polish chemist Ignacy Lukasiewicz setup the world’s first mineral oil refinery in Ulaszowice Poland to produce kerosene at scale. This was less than 900km from Munich and Augsburg where Diesel was developing his engine. Germany had no native mineral oil production in 1895, as of today they only rank 62nd in global mineral oil reserves. Kerosene was a natural fuel choice, it was relatively abundant and nearby.
Diesel had previously experimented with ammonia while working with Linde. Linde used ammonia as the refrigerant in his systems so Diesel was familiar with this gas. Concentrated ammonia gas or liquid is both toxic and hazardous. It would have been available from the distillation of coal, and Diesel was familiar with ammonia during his earlier experiments with Linde. Diesel does mention this as a fuel choice in his patent.
Diesel also considered Coal Dust “Pulverulent solid fuel” which Germany had in supply and probably on a large scale, but as we know today it proved impractical in many applications and would have poor emissions. Germany ranks number 7 in global coal reserves today. Anthracite coal was the national fuel of choice, as it was readily available. He did spend a fair amount of his patent discussion on the fuel supply and injection system for pulverulent solid fuel.
It is very clear that Diesel did not want his patents to specify any one fuel, but rather show how many different fuels could be used. He most commonly used the generic term “fuel”, but here are some other options he discussed; Neutral Gas, Pulverulent solid fuel, anthracite, gas, fluid fuel, petroleum and ammonia vapour. He relied on mechanical variants of the Bunsen burner to distribute fuel for an even burn inside the combustion chamber. His universal fuel claim is that his engine can burn "any kind of fuel, whether solid, liquid, or gaseous."
His second US patent titled “Internal-Combustion Engine”, focuses on the mechanism unique to each fuel choice. (US 608,845, August 1898). Rudolf is the inventor, but this time the rights are assigned to “The Diesel Motor Company of America, of New York”. This patent was previously filed in Spain, France, Belgium, Luxemberg, Italy, England, Switzerland, Germany, Hungary, Austria, and Denmark. Diesel used the Attorney “A Faber du Faurf".
This second patent is clearly about the mechanisms to accommodate different fuel types. There is absolutely no mention of any lubrication system the mechanical device needed or the oils it would require. This is par for patents to stay focused narrowly on the claims, but even the drawings showing many moving parts and contact surfaces are devoid of any oiling system components such as zerks, oiling ports etc.
Figures 1 and 2 Show the Pressure-Volume Diagram with constant temperature lines and the Diesel Cycle. The ideal cycle as you recall is the Carnot Cycle. Figure 2 shows how the injection of fuel at pressure can alter the Carnot Cycle to improve efficiency. Although not shown, the x-axis on these graphs is Volume, and the y-axis is Pressure. The curved lines from 1-2 or 3-4 are lines of constant temperature.
Figure 3 is a cutaway section of an engine to show the fuel-feed mechanism. Mixing of the Fuel occurs prior to entry into the cylinder. Figures 4, 5, and 6 also show varying fuel-feed methods where the fuel is mixed in the cylinder.
C-Cylinder, P-Piston, V-Air Valve, D-Nozzle dictating 2-3 behavior on the above figures, n-needle valve, T-Hopper to contain Pulverulent solid fuel, r-rotary distributing valve, L-Gas Tank with compressed gas pressure(air, combustible gas or a mixture), m-inlet gas pipe, L is connected to C by pipe S and Hopper T, R-Pressure Regulating valve, B-Counterweight to adjust pressure in Cylinder, Q-connecting rod, Governor (not shown) connects to the rod Q. Also Diesel notes that one could use liquid fuel in the hopper T. K and V are not explained in the Patent, but it appears that K is some sort of modified piston bowl and V is an exhaust valve.
Figure 7 shows different nozzle (Bunsen Burner tip) designs to evenly distribute fuel into the combustion chamber. Figures 8, 9 and 10 show the mechanism for operating the injector timing and duration. Figure 9 shows a more complex mechanism to operate valve Y found in Figure 8. At the end of the mechanism of Figure 9 is a large Bevel Gear to finally connect the diesel motor and the horsepower it generates to a machine. Like a car, boat, truck, airplane, water pump, etc.
Figures 11, 12 and 13 relate to the different bunsen burner arrangements inside the piston.
The patent very much demonstrates the claims for Diesel's mechanical ideas the ongoing research and innovation of the diesel engine is all about the Carnot cycle at the heart, and improving injection, timing and more to optimize performance. Today emissions have caused fuel innovation to make Ultra Low Sulfur Diesel (ULSD), Bio-Diesel, and Synthetic Fuels. Pulverized coal - just did not happen.
PS. Nobody is perfect, and if you read the Patent carefully even Diesel had a few of the figures mixed up with their descriptions. Oops!
Diesel was looking to maximize efficiency and get as close as possible to the theoretical limit of the Carnot Cycle.
Diesel envisioned a wide array of possible fuel options, many more than just the "diesel fuel" we use today
Diesel outlined a variety of burner designs and arrangements to accommodate the diverse fuel options
Andrew Prestridge | November 17, 2020
The name "Hydraulic Oil" is somewhat of a misnomer as the root of the word hydraulic, "hydro," means water. While water was the original hydraulic fluid, any fluid that conveys power may be considered a hydraulic fluid. The use of water as a hydraulic fluid dates back to antiquity as many cultures controlled the flow of water for irrigation.
However, using oils in hydraulic systems has distinct advantages in lubricity and has led to their widespread adoption. Hydraulic oils are commonly used in mechanical systems to drive movement. Your car's power steering system is hydraulic, large construction equipment like backhoes and road graders have extensive hydraulic systems to enable large moving arms and surfaces, and aircraft flight control systems are hydraulically actuated. These oils are continuously recirculated in machinery and are not burned. They can be recycled when maintenance or service life occurs.
A suspended oil droplet forming a pendant shape
Hydraulic oils, when put under pressure do not change their density and are known as incompressible fluids. Because they don't compress, forces are transmitted through the fluid with minimal losses. Both water and hydraulic oils are incompressible, but hydraulic oils are used because they also have the property of lubricity to aid in the sliding of major components, sealing, and reducing corrosion. This property allows them to be pumped into cylinders, like the one seen below and with the opening and closing of their outlets, enables the extension and retraction of the rod with the yellow eye.
Cutaway view of a hydraulic actuator
Applications vary somewhat, but the fundamentals of a hydraulic system are pretty basic.
Once the movement and work is done, the rod returns to its initial position and the fluid is recirculated back to the tank at low pressure. The motor to drive the pump can be electric, internal combustion, or diesel.
Schematic of a simplified hydraulic system
The Original Equipment Manufacturer will always specify oils for use in their equipment. Brand names can be confusing but the common design characteristics are viscosity, the operating temperature range; online tools and charts can help make these comparisons across brands easy. Hydraulic oils also need to: keep their viscosity over the operating temperature range, stay liquid (that is, they should not boil, freeze, or generate foam or solids under operating conditions), and should not be corrosive. To get into the details, visit oilviscositychart.com. for more information on hydraulic and other industrial oils.
In some cases it's helpful to send in a sample of your oil to get tested and receive a professional analysis. Up front it is important to choose the oil to meet your machines requirements. Key oil design characteristics for oils are its viscosity, operating temperature range, and essentially operating velocity, which can be easily determined at oilviscositychart.com. And later at service intervals it is important to sample and analyze your oil which can be very indicative of remaining service life. Equipment varies, but trace elements of additives, wear metals, and other contaminants can be determined by a good analysis to guide maintenance.
There is a lot to consider for your particular application as seen above. Synthetic and specialty hydraulic oils will be more expensive but tend to perform for a longer maintenance cycle. Comparable and more standard hydraulic oils range from $10.00 to $13.34 per gallon for a 5-Gallon Pail. Liquids are heavy, so if you can find a local supplier, you can skip a large shipping fee. Expect to pay more for smaller quantities, and generally less for larger quantities. The main ingredient is refined oil and it is derived from produced mineral oils which are trading at around $42/(42-gallon Barrel) or about $1.00 per gallon. As you can see the premium for refining, packaging, marketing... and delivery is high
Any fluid, oil or water, that conveys power is a hydraulic fluid
The most common application are hydraulic cylinders that extend or retract on industrial equipment
There are countless brands and providers of hydraulic fluids at different blends, prices, and qualities
Andrew Prestridge | September 10, 2020
It’s a common refrain heard from the designer, to marketer, to the parent trying to put together their kid’s toy at 3am to avoid ruining yet another Christmas. But putting aside questionable design (and life) decisions, we’ll address a variant of the oh-so-common remark: “there are too many screw options.”
Visiting your local hardware store, popping open the Machinery’s Handbook, or flipping through a McMaster-Carr catalog, you’ll quickly see there are thousands of consumer options for screws and bolts. From the tiniest #0000 (only 0.021” across!) to a 2.5” heavy-duty bolt, there’s a size for every occasion, and a screw pitch to match. Or rather, several pitches. A quarter-inch screw might have 20 threads per inch, or 28, or 32. Metric sizes are no escape either, as M8 screws come in your choice of 1.25mm, 1.00mm, and 0.75mm pitch.
An assortment of different machine screws
Choosing between three or more options, for something that has absolutely no impact on so many designs, feels like an unnecessary headache in the design process.
Having said that, there was a time with simultaneously more and fewer options. Prior to the 1840s there was no universal standard for thread pitch - every manufacturer was left to their own devices. In a way, any screw pitch you could make, you could use and no one would have grounds to complain. At the same time, the product designers of the time had no readily available standards to pull from or common choices to pick between.
Naturally this led to severe fragmentation and millions of incompatible screws, nuts, and bolts - each slightly different. Larger companies narrowed in and developed their own internal guidelines, but these lacked the reach and accessibility of a singular standard. That was the case until Joseph Whitworth took the stage in 1841.
Portrait of Joseph Whitworth, 1846. Artist unknown. [1]
Joseph Whitworth developed a screw thread design that was adopted by major English railroad companies and quickly spread across the country. His papers on screw threads exposed the “evils” of figuring out thread pitches without a uniform standard. While Whitworth admits that any standard would be based on largely arbitrary decisions, and there would always be special cases that don’t fit the standard, he cautions that there is more to be lost by delaying and urges the attention of engineers across the nation. With the support of the railroads, then the Royal Dockyards and shipping companies, Whitworth’s 55-degree thread, with rounded edges and simple table of pitches spread nationally.
Diameter (in) |
1/4 |
5/16 |
3/8 |
7/16 |
1/2 |
5/8 |
3/4 |
7/8 |
1 |
... |
4 |
Threads per inch (TPI) |
20 |
18 |
16 |
14 |
12 |
11 |
10 |
9 |
8 |
… |
3 |
While these pitches are familiar and survive today, the thread shape has not. Excerpt from Joseph Whitworth's "A Paper on An (sic) Uniform System of Screw Threads," 1841. [2]
From there, the British Standard Whitworth thread spread to the US and Canada, and further globally. However, by the 1860s Whitworth’s admittedly arbitrary decisions were already being challenged. In 1864 William Sellers proposed changing to an easier-to-produce 60-degree angle with flat-topped threads instead of rounded.
"Graphic Representation of Formulas for the pitches of Threads of Screw Bolts," William Sellers, 1864. [3]
These changes saw the creation of United States Standard (USS) thread and opened the proverbial floodgates for competing standards. Soon after, thread standards were extended to National Coarse (NC), National Fine (NF), and a litany of metric thread alternatives. As the rate of manufacturing increased and more and more products were developed under each thread standard the age-old argument against change grew more powerful: it was too expensive. Tooling to make screws of each thread were expensive, and once it reached a critical mass, manufacturers were reluctant to spend more capital to upgrade to the latest “standard.” Over the years, international efforts have helped rein in the number of options (3 doesn’t seem as bad as the 20+ that have been developed), but nothing is quite as sweet as the two decades in the mid-1800s that started to converge on thread universality.
[1] Retrieved from Art UK: https://artuk.org/discover/artworks/joseph-whitworth-18031887-179915/search/keyword:joseph-whitworth
[2] Whitworth, Joseph. A Paper on An Uniform System of Screw Threads, 1841. Retrieved from Wikisource: https://en.wikisource.org/wiki/Miscellaneous_Papers_on_Mechanical_Subjects/A_Paper_on_an_Uniform_System_of_Screw_Threads
[3] Sellers, William. Graphic Representation of Formulas for the Pitches of Threads of Screw Bolts, 1864. Retried from Wikimedia: https://commons.wikimedia.org/wiki/File:JFIScrewThread300.png
Screws were custom-made by individual machinists for local applications
Whitworth proposed the first standardization to unify screw threads
While there are still varieties (inch v. metric, coarse v. fine) screws are generally standard
Andrew Prestridge | October 29, 2020
Tribology may be an unfamiliar word, but it’s a familiar topic. Tribologists study the interaction of sliding surfaces, specifically for friction, wear, and lubrication. Any time objects are in contact and moving, two things are happening: there is friction, and there is wear.
As a society, overcoming these two phenomena consumes 23% of all energy generated on the planet. Overcoming friction alone accounts for 20% of all energy generated, and building and replacing worn out components (worn out from the friction) amounts to the other 3%. You can read more on the scholarly article by Holmberg and Erdemir here.
Chalk – a product designed for friction and wear
One of the simplest ways to reduce wear is to reduce the physical contact between objects; a piece of chalk lasts longer when waved through the air compared to drawing on rough concrete. To be fair, flailing about with a piece of chalk in your hand won’t make a beautiful drawing, but at least the chalk won’t get any smaller. Soft chalk rubbing on hard concrete offers a highly magnified view that exaggerates some of what is actually happening on the microscopic level between all moving surfaces.
Tiny bits of material are transferred from the soft material to the hard material, or is lost to the surroundings. This process accelerates as more load is applied, and one can imagine the consequences of running heavy-duty processes continuously, as is found in the gearbox of your machines, or between pistons and cylinders in your automobile engine.
Unfortunately for these machines, they often don’t have the option of running in air, not contacting anything. Just as the chalk in air won’t leave a mark, a gear spinning freely does not transfer torque. It would appear that the excessive wear from solid-to-solid contact is an inevitable consequence of doing work. However, there is an alternative: using liquids as lubricants.
Liquids are largely incompressible, so a force applied at one end can be transmitted through the liquid - this is the basis for how hydraulic systems work. In a well-designed gearbox, none of the gears are in direct contact with each other; a thin layer of oil separates the two gears and prevents them from ever actually touching.
This separation provides key advantages to the moving gears: greatly reduced wear, reduced friction, heat dissipation, and a less hostile environment for metal components. With the gears not actually touching, and instead transmitting force through the liquid intermediary, there is much less occasion for metal-to-metal contact of the tooth surfaces.
Comparison of low and high viscosity fluids
Oils reduce friction, however there may be an increase in drag depending on the viscosity. The liquid lubricant is also far superior at transferring heat away from the contact zone, keeping the components cooler. Oils lubricate and they also displace water to prevent rust and corrosion, keeping metal components intact and with a smoother finish for longer.
While adding a small amount of a lubricant leads to a steep drop in friction, after a certain point the extra fluid begins to increase the effective friction in the system. This effect, known as the Stribeck Effect, is amplified for higher viscosity oils and equipment moving at faster speeds.
Schematic view of friction between surfaces as relative speeds increase. The result is greater separation between surfaces, and consequently a thicker oil film [1]
In some cases it's very helpful to send in a sample of your oil to get tested and receive a professional analysis - Up front it is important to choose the oil to meet your machines requirements. Key oil design characteristics are viscosity, operating temperature, and essentially RPM, which can be easily determined at oilviscositychart.com. And later at service intervals it is important to sample and analyze your oil which can be very indicative of remaining service life. Equipment varies, but wear byproducts show up in the analysis guiding preventative maintenance programs.
While it may not be difficult to wipe up some excess oil, it's important to use a lint-free cloth while cleaning inside mechanical equipment to avoid introducing fibers or other contaminates into the system. While some extra oil adding drag may be a problem, cloth fibers clogging an oil line is a big problem. Other solid contaminants are just as problematic, keep it as clean as possible.
As always, be responsible and recycle your oil. Check out Napa's guide on disposing & recycling of used oil for some best practices and helpful tips
Solid-to-solid contact introduces friction and causes the solid surfaces to wear
Introducing a lubricant layer (usually an oil film) reduces friction and reduces wear
Liquid films introduce drag, with higher viscosities creating higher drag
PS: The technology for a nearly frictionless “Air Bearing” exists and is used in modern turbine systems.
PS2: WD-40 is a solvent, it is not a lubricant.
[1] Robinson, Joshua & Zhou, Yan & Bhattacharya, Priyanka & Erck, Robert & Qu, Jun & Bays, J. & Cosimbescu, Lelia. (2016). Probing the molecular design of hyper-branched aryl polyesters towards lubricant applications. Scientific Reports. 6. 18624. 10.1038/srep18624.
Andrew Prestridge | September 16, 2020
The American Gear Manufacturer's Association, AGMA, is the global network for technical standards, education, and business information for manufacturers, suppliers, and users of mechanical power transmission components.
As associations go, AMGA is small with only 500 Corporate Members, 21 of which have been members for over 50 years. After founding in 1916, AGMA held its first annual meeting in May of 1917, in Pittsburg, Pennsylvania. Today their headquarters are in Alexandria, Virginia.
The logo for the American Gear Manufacturer's Association
In 1916 gear manufacturers came together to form AGMA, and the reason was two-fold: generally for standardization, but also specifically to get timing gears in auto engines to run silently. Remember that the first hobbing machine patent to manufacture gears was granted in 1856, but it was not really pushed into service until the late 1800s.
Henry Ford raised the demand significantly in the early 1900s and the race was on in the automobile industry, and by extension the gear industry. At the time AGMA was being formed Ford, Willys-Overland and Buick were the best-selling auto brands. None of the automakers were founding members, but all the major gear manufacturers were present.
As active members of AGMA, we've been able to use this access to incredible people and standards to tackle a range of different gear projects. If our expertise could be of help to a project you're working on, feel free to reach out and we'd be happy to point you in the right direction.
AGMA is accredited by the American National Standards Institute (ANSI) to write all the gear-related US Standards. ANSI was founded only a year later in 1918, so it appears the mid-1910s were a solid decade for standards and technical associations, likely due to the influx of global conflict.
AGMA is involved globally as the Secretariat (Chairman) for the International Organization for Standardization’s (ISO’s) Technical Committee 60 on gear standards. The ISO is the most prolific international standards-setter despite being relatively late to the game and founded in 1947, coincidentally in the midst of another global conflict.
While gears are hidden from our eyes in most daily use, they make our world move. During these difficult times AGMA is anything but hidden, they are still pivoting and being flexible to adjust and provide their services to gear manufacturers. As they say of trade associations, crucial in normal times, vital in a crisis.
Especially vital is the use of standards to keep track of the complicated geometry of gears. Having a gear tooth geometry based on the involute curve enables special and specific characteristics, like rolling without slipping, but adds complex mathematics. While these complexities are present in spur gears, they further compound with helical, bevel, and more advanced gear geometries. To that end, AGMA keeps it all straight with clearly defined standards and references.
AGMA serves the small, but close-knit gear-making industry
AGMA is the leading provider of international standards for the gear-making community
While AGMA itself is over 100 years old, many of the current members have been involved for over 50
Andrew Prestridge | September 8, 2020
The invention and perfection of the involute gear is one of the least heralded advances in mechanical engineering. Due to their essential function (transmitting torque and movement) they are hidden deep inside castings or shrouded with protective covers. Out of view, the modern gear is doing more than ever as we have challenged designers to transmit more torque, in lighter packages, while running quietly, and at the same time cost less. Luckily, good designers, materials, and better and more accurate gear processing equipment have been able to continue this path for high-end applications.
Finite Element Model of a Spur Gear
But what if you don’t work for GM, Ford, Chrysler, Tesla, or Big Industry? How could an individual possibly take all the accumulated millennia of knowledge and make their own gears? How can the Maker Movement include gearing in their toolkit? How can we get a grip on gears that have many tall hurdles and slippery rabbit holes where one can get lost?
CAD and machine tools have been rapidly increasing in capability and decreasing in cost, so the ability to mill, route and 3D-print gears is in reach to a larger audience. So how do I get started? Here are some simple answers:
If you own a 3D-Printer, it comes down to finding a file (.DXF, .SFG, .STL, .STEP, or others) of a gear that you would like to print. We created a free gear generator for your use. The next step is setting up the center distance between two gears you have printed to get them to mesh properly. You can do this through a calculator or by feel like most watchmakers.
If you own a CNC router, the pathway is identical to the 3D-printer process, use a compatible filetype (2D or 3D), load a sheet of plywood/plastic/brass and you are on your way.
Just knowing the terminology “involute” you are way ahead. This is the shape of the meshing gear surface that allows gears to roll (and not slide!) The rolling characteristic of gears is a realization in history dating back to at least 1500AD and involves the famous mathematician Euler. This is where the math starts to creep into the making process and this is the first big hurdle. If you cannot find your gear online in a format you like, you may want to create one from scratch with a CAD program. The formulas are actually not too difficult, and you can make a parametric set of variables that will draw gears of any tooth count.
This is usually the hurdle that is steep enough to halt most in their tracks. And you must know it if you are to design the gear blank dimensions for many processes. Our Gear Dimension Calculator in conjunction with the Measurement Over Pins calculator will enable you to make gears AND QC them so you can dial-in your process.
Measurement Over Pins - A Key Quality Metric
This is the next step in the understanding of gears and relates to backlash, profile angle, gear mesh etc. These variables allow designers to make enhanced designs for gears that lead to stronger and quieter gears in mesh. This is the start of another level of skill that you can learn more about in our MOP blogpost.
Process Equipment | Drawing of Gear Outline & Tooth Count (involute is in the drawing) | Involute is in the cutter | Gear Blank Dimensions | Knowledge of Pressure Angle, Tooth Count, Tooth Form (Involute | Profile Shift Correction, or Addendum Modification on Specification | Machine Tool Setup, CAD/CAM Toolpath |
3D-Printed | YES | NO | NO | NO | NO | NO |
CNC Router | YES | NO | NO | NO | NO | NO |
Watchmaker, lathe, files | YES | NO | YES | NO | NO | NO |
Manual Mill | YES | YES | YES | YES | NO | NO |
Manual Shaper | YES | YES | YES | YES | NO | YES |
CNC Mill | YES | YES | YES | YES | YES | YES |
Gear Shaper | YES | YES | YES | YES | YES | YES |
Gear Hobber | YES | YES | YES | YES | YES | YES |
Gear Grinder | YES | YES | YES | YES | YES | YES |
CNC Gear Hobber | YES | YES | YES | YES | YES | YES |
CNC Gear Grinder | YES | YES | YES | YES | YES | YES |
Bold-Italic: Our Spur Gear Generator creates the .DXF and .SVG files for upload into your machine or CAD/CAM program.
Bolded: Our Gear Dimension Calculator solves Involute math for you and is helpful in these areas of gear processing.
*Making plastic gears from a mold is a process, but the mold making of the original gear originates from one of the above processes
Using a gear generator is the easiest way to make a gear without specialized equipment
Machine tools may have bits or cutters that have the involute gear form built in
Using Measurement over Pins can tell you if your gear is the right size and shape
Andrew Prestridge | May 4, 2020
Gears are everywhere: your car has many in the transmission, engine, rear end, and other mechanisms, your old mechanical electric meter has a watch-like gear-train to keep track of the electricity you used each month, bicycles have chains and the sprockets are a special form of a gear and the list goes on. Frequently the gears are hidden from view for lubrication, safety and other reasons. To the untrained eye, they are just gears, but there is an accumulation of innovation in geometry, materials, engineering, vibration, lubrication and much more to design the modern gear. The modern world demands transmissions full of gears to be lighter, quieter, smaller, more reliable and less expensive than their previous models.
The vast majority of gears are made with the hobbing process as it is very efficient and inexpensive compared to other methods. A gear starts out like a donut of metal, called a gear blank. The cutting tool is called a hob and it removes the material in between the gear teeth. A hobbing machine holds the gear blank and the hob in the correct geometry and for every rotation of the gear blank, the hob must rotate X times to make an X-Tooth gear. The hob passes across the face of the gear blank removing material while both are turning.
Mr. Christian Schiele, of Lancaster, England recorded British patent number 2896 in December of 1856. The work made quiet history as the first gear hobbing machine patent. If you read the patent it looks like the hobbing machine was added at the end, sort of a bolt-on section; a last-minute edit. The hobbing process for making gears is still used today and the vast majority of industrial gears are still made in this manner.
Early machinery was typically built to be bench-top sized, or small "parlor-style" machines with wooden legs like ornate parlor furniture. Later, as more horsepower became available to machinery and forces increased, so too did the need for rigidity. Machine builders quickly changed designs from ornate and almost dainty wood to large and robust cast iron.
Drawing of Schiele's original hobbing machine, featuring rigid anchors
The patent drawing on Sheet 2 clearly shows a gear hobbing machine design much more rigid than a parlor chair with four angle-iron legs bolted to the floor with a large wheel in the middle. But while Schiele’s machine has surpassed the limitations of parlor-style, the design is still a long way from the rigidity one would expect from a modern machine. More importantly, the drawing shows a hob and all the parts of a functional hobbing machine.
The patent claims the machine can make gear teeth on “toothed wheels” (spur gears) and “oblique wheels” (bevel gears). Robert Hermann Pfauter, who dominated the gear manufacturing market with his universal hobbing machine in the early 1900s, would openly refer to Schiele’s patent as the first patent for a hobbing machine. Sadly, the drawing is all that we have from Schiele’s efforts as no prototype or physical relic exists.
Schiele was living in Lancaster when he submitted the patent, but he was originally from Frankfort, Germany. Records indicate he had arrived as early as 1847, nine years prior to recording his hobbing machine patent. Apparently, he had come to Great Britain to be a part of the industrial revolution and "collect patents." In that regard, he succeeded as a copious inventor and was granted over a dozen patents spanning mechanical topics from pumps and fans to engines and ventilators.
Interior of the Great Exhibition of the Works of Industry of All Nations
As a bustling entrepreneur, he had a machine shop full of water pumps and other jobs to fund his patent collecting. His interest in technology spurred him to present at the Great Exhibition of the Works of Industry of All Nations (Great Exhibition) held in London's Hyde Park in 1851 where he may have seen Prince Albert and most certainly experienced the Crystal Palace. A few years later he presented at The French Exposition Universelle held on the Champs-Élysées, Paris in 1855. He was in rare mechanical engineering company at both events where Joseph Whitworth, famous for standardizing screw threads, also presented. Whitworth specialized in threads, Schiele in gears. The men's amicable relationship is known and referenced by the historian Robert Woodbury.
In the end, Schiele could not convert the Patent to a physical machine or monetize the idea. He declared bankruptcy in 1865 and returned to Germany where he died in 1869.
Sheet 2 from Schiele's 1856 patent. Thanks to the help of Rupert Lee of THE BRITISH LIBRARY for this drawing, April 2019
The "cutter" as Schiele calls it is called a "hob" in modern terms today. Although it is shown on Sheet 2 it does not get a Figure number or even a letter callout like 'a' or 'b'. Plus it gets little attention in the patent, maybe only one sentence. As we know today, the hob carries the DNA of a modern gear tooth geometry. It is called the Involute shape and it has a very special quality.
The most prominent early hobbing machine tool builder was Hermann Pfauter. In his book, Hermann gives full credit to Schiele for his patent as prior art. [5] The Pfauter patent appeared 31 years after the passing of Schiele. Part of Pfauter's resume included work at the Reinecker factory where manual and one-gear only hobbing machines existed to make gears for their grinding machines. The hobbing and grinding process knowledge served Hermann well in machine tool building and in his equally amazing hobb cutting tools.
Pfauter's prototype hobbing machine
Hermann significantly progressed the hobbing machine to be more universal and make gears of any tooth count, spur and helical gears, as well as worm gears. The true love of his work shows in the craftsmanship of his machines. He had aspirations to sell machines in the United States, but his untimely death shifted the dream to a future generation. His son Herman Pfauter created Pfauter-American and was making great progress in the 70's before catching the eye of Gleason Corporation. Gleason, based in Rochester, NY, is best known for their bevel gear machines and cutting tool technology.
Gleason HCD 400 Hobbing (Chamfering, Deburring) machine
Gleason is one of those companies that is proud of their history and the acquisition of Pfauter was like a marriage of two families much more than a corporate takeover. Technology, automation, a long history of innovation, high quality machinery and tooling comes from Gleason this day.
1) Schiele Patent of 1856 (Includes the full Sheet 2)
3) The Great Exhibition of 1851 British
4) Exposition Universelle of 1855
5) Pfauter, Hermann, Pfauter-Wälzfräsen (Pfauter Hobbing), Springer, 1976. Softcover ISBN 978-3-662-12682-0
6) With the assistance of Graham Hicks of Ancestral Stories, Spring 2020
7) Woodbury, Robert, History of the Gear-cutting machine, 1958, Technology Press MIT
Christian Schiele recorded the first patent for a hobbing machine in 1856
Schiele's design features a robust mounting, a departure from dainty wooden legs
The final sheet of the Schiele's patent was long thought missing or incomplete
Andrew Prestridge | November 13, 2020
Gears have a special place in the mechanical world, they make things go, move, or rotate. They are also hidden from our view as they need a case to hold their distance precisely together while rigidly on their shafts in a bath of their favorite lubrication.
The NASA Reference Publication simply titled "Gearing" is a very complete summary. The sections range from History, Life, Lubrication, and end up with Transmissions. It is a great reference for anyone practicing the mechanical trades and is free to download here. Some gears are great for transmitting torque, some are great for very high gear ratios or keeping track of angles. All of the general and some very specific relationships are in "Gearing".
Even if you are not designing or repairing gears, they have a very interesting history. The NASA Gearing publication has one of the better history recaps. We have used gears as the focus or our article and timeline 5000 Years of Gears where you can get a more in-depth review of the people that are part of the story of gears. Early uses for gears include navigation, timekeeping, pumps, and calculators. Longitude was conquered using a geared clock mechanism.
When designing a transmission there are many factors to consider. The relationships of different gear types are spelled out. Gear ratio ranges for the various types of gears, amounts of torque that can be transmitted, and more is discussed. No need to re-invent these well known relationships when you are feeling innovative. The crossed-helical pair shown below allows the motion from one shaft to be turned at 90-degrees and transmitted into another.
The fundamentals of gearing are pretty clear, but due to their special rolling characteristics, the use of geometry, number of variables and equations gets complicated in a big hurry. The image below shows the basics that are considered the minimum to describe the most basic spur pinion and gear combination.
If you have driven or ridden in a car, you have experienced the gear reduction of a transmission. Cars engines have an RPM capability that is too high for the gear train and rear drive to the wheels, so the transmission reduces this RPM significantly using first gear. For most transmissions like a manual 3-speed, 1st and 2nd progressively increase the RPM to the rear wheels and then the final 3rd gear all the engine RPM is transmitted to the rear wheels and used for highway speed which is a 1:1 ratio with the motor.
The engine of your car lines up with the transmission and then the driveshaft to the rear-end. The torque and power transmission needs to simultaneously transmit to your right and left rear tires. The big pumpkin shaped round part at the center of your rear-end is really another transmission that accomplishes this task and it is called a differential.
Given all the different gear types, there are many ways to transmit, turn or rotate mechanisms. Knowledge of gears and how they are designed will help you repair, design or maintain machinery.
Gears surround us in the modern world, even if we don't always see them
Gears control the speed, torque, and direction of shafts and rotating components
As gear complexity rises, institutions like NASA develop more thorough guides
Andrew Prestridge | September 13, 2020
Screws, bolts, nuts, washers and their diameters, lengths and pitches take considerable effort to design correctly. While a quick build might get away with using whatever you have around the garage, when it counts you need to make sure to get it right.
When it does matter, there is a lot to consider: material selection, coatings, and vibration resistance are just the start. Here is a starter list:
Choosing a screw head is one of the steps
If any of this sounds familiar or you have any of these questions, it’s likely it’s been analyzed by the engineers over at NASA. If there’s any place where it matters most to get it right, it’s space. Not only could a sheared bolt be lethal, but there’s no hardware store or provision for a quick replacement if something fails.
Fortunately, they’ve put together a handy resource, the NASA Fastener Design Manual from 1990. This is one of those evergreen documents that keeps giving useful information decades after its publication. It’s a valuable fastener guide, but it is the beginning of a very deep rabbit hole so watch out. We have busted our knuckles, had things break at the wrong time, cussed while removing a nut from a long-corroded bolt (and sometimes just cut it off). It is a surprisingly useful document and short enough to review at least once for your earth-bound and mars-bound projects.
For those serious designers, makers and builders, the NASA Fastener Design Manual will give you a very complete perspective on all that should be considered for fastener design. A very useful check on your design chops is to review your old projects and test them-honestly. Ours showed bolts that were too large for the load, had expensive threads, would have been better with washers and worse.
For those of us with more of an artistic flare, it also ends up being useful. You may take a while to open all the boxes in a hardware store to see what is available, but the guide can give you a detailed overview for each. Is it complete? No. Fasteners are like software, they are getting improved all the time. But the most common are explained in detail.
I know most of you don’t want to read the whole fastener design manual, so we’ve taken one for the team. To hopefully spare at least one soul from a headache or frustration, here is a summary of tips from the guide and our experience with fasteners.
It’s best to know the purpose, dimensions, and pitch for your fastener before you go to the hardware store. Bringing a sample of your nut, bolt, and washer will certainly come in handy. All the screws start to look the same when you’re staring at a wall of 4,000 of them: different designs, different uses.
Always use some sort of lubricant if you’re going to be taking something apart more than a couple times. My favorite is Never-Seez on machinery that will require future maintenance. It makes it easy to remove the bolts, especially if they are in a corrosive environment. You can pick some up at your local hardware store or on Amazon for pretty cheap. For those that live along either coast, ocean air is surprisingly corrosive. And in the case of stainless steel hardware it has a bad characteristic of galling without lubricant even when the fasteners are new. Check out our blogpost on galling for more details.
The design manual was originally published in 1990 and the list of thread lubricants proudly shows the brand name Never-Seez. It beats all other options with a useful design temperature limit of 2,200 °F.
Machinists and metal workers will love the manual, but the principles work for all materials. Give it a close look! Before threads many larger metal structures were held together with rivets installed by blacksmiths. Inserts are a great way to hide the nut. They are an additional piece of technology to design for, but they can yield great artistic results for your project while still giving the joint proper clamping force.
The history of threads and pitches is pretty interesting. The ancient and current processes for making threads is pretty interesting too. If you want to know more, check out this article on a gentleman by the name of Whitworth who was instrumental in the earliest "standardization" of thread pitch. The guide is no help in these areas.
The average hardware store split-washer, aka a helical spring washer, is not a locking device and the nut can still come unscrewed. This washer acts like a spring until you tighten it down, then it transforms to a normal washer.
Despite their appearance, once these washers are tightened they do nothing to prevent loosening
There is etiquette for how many threads should show past the nut: as few as possible. One or two threads for fasteners smaller than ¼ inch diameter is fine. Anything more is “wasteful” and your future self will not like the extra work required to remove the nut once that long bolt has corroded. These long bolts usually stick out too far where they should not belong and the risk of injury increases. When you look at very well designed machines, the fasteners are a perfect fit. Even though your project or prototype may be done in a rush to capture your new idea, properly designed fasteners can be a source of pride that may actually speed you forward. Spend most of your time on the idea, plan a little time for fastener considerations and it will make your life easier.
It happens. You over-tighten a hardened bolt in a softer aluminum and the threads strip. Or a bolt snaps off down inside a hole, followed by the machinist tricks to drill out the bolt. Again, this can leave you with a larger than stock hole. The application may still limit you to the same size fastener and the Heli-coil or Threaded Insert comes to the rescue.
Installing a Heli-coil
Lockwiring for fasteners occurs in critical applications, most commonly in the aerospace industry where a failure is just not an option. The process is manual, tedious, but very effective. A wire is used to make sure the fastener heads cannot rotate once installed. The process can be done on both fastener heads and nuts.
Lockwires holding screws and nuts in place
If it is a critical application, DO NOT REUSE THE FASTENERS. It’s better to grab an extra pack at your local hardware store, than to have something fail in the future due to old or worn components. Your instruction manual should tell you if this is the case, but when in doubt, throw it out. These situations are usually easy to spot and usually the Original Equipment Manufacturer (OEM) will label them clearly on drawings and sometimes even near the fastener. A few machines come to mind: cranes, gondolas, elevators, airplanes and space ships. Basically when a human life is at stake, it is a good idea to make certain of your fasteners.
Too much Torque on Small Fasteners is a problem
With small fasteners, It is very common mistake to over-torque them and have your screw break off in the hole. The smaller they are the harder they are to remove - be careful tightening them past their purpose. Those tiny screws in eyeglasses, or holding together your cell phone come to mind.
Rivets are fasteners too.
A whole range of rivets, waiting to be remembered as a quick choice when picking a fastener, sometimes it just takes a little getting started.
Our list may not get you to space, but I hope it helped you save some time. The NASA Fastener Guide has some extremely valuable reference material and is some of the more impressive technical art you will see (that’s right – most of it was done by hand)
The more you know about your application the better you can specify your hardware
Split washers look like lock nuts, but don't help once tightened
When your application is critical, don't try to save money reusing fasteners; it's not worth the risk!
Andrew Prestridge | September 8, 2020
A clear night view of the visible stars was the first IMAX theater.
This evidence has been visible since we first walked the planet. It is indesputable, it is a fact.
History can be verbal, written, or exist in artifacts of known dates. We have too much of the first two, and not enough of the last. Our observations of the heavens, natural curiosity and many centuries of evolution has given us gears.
The earliest history. No artifacts remain, written accounts only.
3000 BC........... Ancient Mythical Chinese Craftsman made a South Facing Chariot
255 BC............. Eratosthenes made the first Armillary Sphere
250 BC............. Archimedes of Syracuse Astronomy, Screw and Worm Gears
200 BC............. Apollonius of Perga, Astrolabe Projection for Navigation
The earliest artifact gears are in the well-known Antikythera Mechanism from 80 BCE. Many have written about the mechanism and their maker who is unknown. We will name this maker The Naburian. The original mechanical engineer, mathematician, astronomer, craftsman and artist. Likely it took a team of people to accumulate enough knowledge and skill to make this artifact. The effort, without question, is extraordinary for any day in history.
Antikythera Mechanism, as recovered from the seafloor
Modern, artistic rendering of the Antikythera Mechanism
The discovery of the Antikythera Mechanism gave us a surprise tangible artifact from the past regarding the mathematical, astronomical, and mechanical skills of the maker(s). No patent office existed to document or claim the design. No historical text records them, and not much comes remotely close until we start to see the geared astrolabes of the 1200s. Observing the heavens, religion, and early Horology helped this early technology along the way with simple cogs and triangular gear teeth.
The makers of gear technology were commonly employed by kings and rulers as astronomical prediction was valuable. Pumping water and lifting loads were also helpful skills to possess. Later gears played an important role in navigation when the Harrison geared clocks enabled the calculation of longitude. Neil Armstrong often visited Greenwich to see the Harrison clocks tic-toc away in the Royal Observatory as he knew first-hand the relationship between accurate time and navigation. Henry Ford was probably the first to harness mass produced gears to transmit power in his vehicles. Fast-forward to today and continuing many traditions, it took a joint GM-Ford research team years to design a 10-speed transmission for fuel conservation.
Honorable mention should definitely go to Ancient China where geared-mechanisms in a South Pointing Chariot are rumored to have existed some 3,000 years ago. Gears are the hidden and ancient technology that our modern world uses every day....and has likely been for 5000 years!
80 BC............... Antikythera Mechanism – Greek Craftsman we call the "Naburian"
1221 AD........... Geared Astrolabe by Isfahan – Oldest functional metal gearing for Navigation and Religious purposes
1330 AD........... Giovani de Dondi, Verge Escapement enabling mechanical clocks
1410 AD........... Prague Astronomical Clock
Prague Astronomical Clock
1503 AD........... Leonardo Da Vinci, Polymath – shows Screws the equivalent of modern worm gearing
1504 AD........... Christopher Columbus, Captain, Navigator, predicts lunar eclipse, oh yea the America thing too
1540 AD........... Juanelo Torriano, Clockmaker writes of having a Gear Cutting Machine, Subject of King Philip II
1545 AD........... Girolamo Cardano, Mathematician, Involute Gear Geometry
1597 AD........... Tyco Brahe, Astronomer, Kepler was his assistant, made many star charts
1600 AD........... Gallileo Galelei, Astronomer, passed down horology to Huygens
1623 AD........... Johanes Kepler, Astronomer, laid the foundation for Newton
1656 AD........... Christiaan Hyugens, Clockmaker, Inventor of the pendulum clock
1687 AD........... Isaac Newton, Gravity - based on a knowledge of how planets interact – through time!
1707 AD........... Scilly Naval Disaster, loss of 2000 sailors due to insufficient Navigational tools – Longitude
1712 AD...........Thomas Newcomen, Mechanic, First practical piston steam engine (with gears) to pump water from coal mines, to stay warm in England.
1714 AD........... British Parliament Prize – The Longitude Act of 1714
1720 AD........... Joseph Williamson, Clockmaker developed differential gear and patent
1739 AD .......... Henry Hindley, Instrument Maker, First Dividing Engine for graduations accurately
Hindley's first Dividing Engine
1751 AD........... Charles Étienne Louis Camus, He really did properly describe the Involute Gear Geometry
1751 AD........... Jacques De Vaucanson, Machine Tool maker, first metal lathe to make larger gears
1752 AD........... Leonhard Euler, Mathematician, Polymath, also Involute Gear Geometry and more
1761 AD........... John Harrison, Clockmaker; In the end he won the British Parliament Prize on Longitude. His work changed Navigation-forever. All he wanted was to work on his clocks in his shop.
1768 AD........... James Cook, Captain, Navigator, British Explorer, sailed the first sea trials with Harrison and his “H4” clock and reported great accuracy.
1768 AD........... Jesse Ramsden, London's Instrument Maker, Marked many Nautical Instruments, his famous dividing wheel is located in the Smithsonian.
1781 AD........... Kästner, Abraham Gotthelf, Mathematician, wrote systematic summation of gearing calculations
1798 AD........... Henry Maudslay, Machine Tool Maker, Father of Machine tools, locksmith. Trained Robers, Napier and Clements who all made significant machine contributions
1835 AD........... Joseph Whitworth, Machine Tool Maker, “Whitworth Threads”, First Hob Patent
1841 AD........... Robert Willis (Cambridge England) wrote "Principles of Mechanism" Sometime in 1810-1820 he standardized the gear pressure angle of 14.5° along with Brown & Sharpe
1851 AD............Great Exhibition, London, 1 May to 15 October 1851
1852 AD........... Patent Office of Britain from the Patents Law Amendment of 1852
1855 AD............Exposition Universelle, Paris, 15 May to 15 November 1855
1856 AD........... Christian Bernard SCHIELE, Inventor, First Hobbing Machine Patent, see patent drawing
Schiele's Hobbing Machine
1870 AD........... Reinecker Machine Tool Company-Germany. Used early hobbing process and machines, sold and moved to Russia. There is very little written about this company and their machines. Date is very approximate.
1874 AD........... William GLEASON, Founder of Gleason Works, exists today as Gleason Corporation.
1881 AD........... Warner-Swasey Co., Machine Tool and Instrument Makers, Constructed large worm gears for Observatories across the USA
1889 AD........... G.B. GRANT, Machine Tool Maker, Spur and Worm Gear Hobbing Machines. His original company spawned Boston, Lexington, Cleveland and Philadelphia Gear Works Companies.
1893 AD........... Rudolf Diesel, Invention of the Diesel Engine
1894 AD........... ACME Thread with an included angle of 14.5° formalized by ACME Screw Machine company of Hartord Connecticut
1896 AD........... Edwin R. FELLOWS, Inventor of the Gear Shaping process and machines, many in use today, and a brand of Bourne & Koch with ongoing support.
1900 AD........... Robert Herman PFAUTER, Locksmith, First Universal Hobbing Machine for Spur and Helical Gears. Pfauter America was Purchased by Gleason Corp. in 1997. Pfauter worked in the Reinecker machine tool plant prior to starting his company.
1901 AD........... Carl Edvard Johansson, Inventory and Scientist. He solved in a very practical way the conversion from inches to meters, and gave us “Jo-Blocks” to make interchangeable parts at great scale.
1903 AD........... Founding of Ford Motor Company. There are only two people in the world that could enter Henry Fords Office without knocking, Edsel Ford and Carl Johansson
1908 AD........... Sam Sunderland, Patent that later Parkinson and then MAAG purchased for planning gears
1913 AD........... Max MAAG, Inventor, Gearboxes, Gear Generators Bevel Gears
1914 AD............First Edition of Machinery's Handbook
1916 AD........... Founding of American Gear Manufacturers Association (AGMA)
1933 AD........... Construction Commenced on the McDonald Observatory designed by Warner & Swasey
1947 AD .......... Invention of the Bipolar Transistor...then computers...just for....automation and modern CNC machinery
1980 AD .......... AGMA recognizes 20° Pressure Angle
2020 AD........... Founding of Evolvent Design, LLC
The South-Pointing Chariot is recognized as the first depiction of a geared mechanism in use, but there are debates on whether it was ever made
The Antikythera Mechanism is the oldest known geared artifact in existence
Researchers discovered the planthopper Issus coleoptratus has gears in its legs to help it jump straight.
Andrew Prestridge | September 8, 2020
Dividing Heads (often called indexing heads) are machine tools used to provide controlled and repeatable rotation to a tool or workpiece, usually as an accessory to a milling machine, grinder, or lathe. A classic and personal favorite in our machine shop is the Ellis Dividing Head, but you can also find a different manufacturer's dividing head that would fit your needs. What makes it work inside the housing is a worm and worm gear transmission. Regardless of the brand they usually come in gear ratios of 40:1 or 90:1. Electronic rotaries (with an encoder and servo, like those found in Haas mills) more often have a ratio of 60:1
Ellis Dividing Head - annotated original image
Dividing heads are closely related to rotary indexers, but with a key operational difference: Rotary indexers use a scale and show the angle of rotation (from 0 to 360 degrees), while dividing heads use pre-defined plates to rotate a fixed amount. These plates are generally circular with multiple rows of equally-spaced holes.
Using a dividing or indexing head requires you to know just how far to rotate the device for the project you're working on. Generally the indexer will jump from one hole to another, so the rotational amount is the same. However, you will need to calculate how many full rotations, and how many holes in which circular pattern to go just the rotation you need.
Fortunately, all of this math can be avoided by following the chart for your device.
This plate can be used either directly, or through a geared dividing mechanism. In direct indexing the workpiece and plate rotate in a 1-to-1 ratio, and holes are used directly. That is, a plate with 12 holes can divide the workpiece into 2, 3, 4, 6, or 12 equal segments. A dividing head incorporates an internal gear ratio (usually 40:1, 60:1, or 90:1) with the same plates. In doing so, the dividing head enables many more combinations than just direct indexing.
For example, imagine a plate with 15 equally-spaced holes and a dividing head with a 40:1 gear reduction. In direct indexing, a workpiece could be divided into 3, 5, or 15 equal segments. Using the dividing head, the same workpiece could be divided into 2, 3, 4, 5, 6, 8, 10, 12, 15, 20, 25, 30, 40, 50, 60, 75, 100, 120, 150, 200, 300, or 600 segments. Essentially, the dividing head acts as if it’s a direct indexer with 600 holes; 15 holes in the actual plate * 40:1 gear ratio. Let’s look at how some of these combinations are possible.
Ellis Dividing Head Indexing Plate #32 - own work
With a 40:1 gear ratio, you’d need to turn the crank on the dividing head 40 full turns to rotate the workpiece once. To get 6 equal divisions, you’d need 40/6 = 6+2/3 = 6.66666 turns. The 6 turns are easy, but the remaining 0.66666 needs the holes on the plate.
If we multiply the partial turn by the number of holes on the plate, we’ll know exactly how far to advance the diving head: 0.66666*15 = 10 holes. Putting these together, to divide the piece into 6 segments you would rotate the dividing head 6 turns and 10 holes.
To get 75 equal segments we’ll follow the same process: 40/75 = 0.53333 turns. Now, there is no full rotation, but 0.53333*15 = 8 holes. So if we rotate the dividing head forward by 8 holes each time, it will divide the workpiece into 75 equal segments.
A dividing head is a great add-on for a mill and opens the door to making gears, splines, bolt patterns, and much more. Most dividing heads allow you to angle the device (and your part) so you can hold your piece vertically, horizontally, or at any angle in-between. Vertical is great for drilling holes on a circle, like for a flange or connection, while horizontal helps for gear teeth and splines.
Check out our video on making a gear with the Ellis Dividing Head here:
Uses continuous rotation and has a scale to read the rotation angle. Subject to measurement error at each measurement
Fast rotation and simple division, but limited range of divisions per plate
More complicated division, but greatest number of options per plate
Andrew Prestridge | November 26, 2020
In 1900 Arthur had a job to do in the shop: drill a bunch of holes. At this point in history, large overhead central power systems with belt drives provided the power for machinery. Making this power connection to his machine, plus chucking up a drill bit into an inferior chuck, caused Arthur to slip and bust his knuckles. There is nothing like a challenge, whether from another person, or a machine, to spur on a solution. By 1902 he had a design and his first patent for the keyed Super Chuck. His first design had a broken part, stationary ball bearings and no screws or pins. Described this way makes it sound doomed for failure, but these cleverly designed chucks have been in use for more than 100 years and are still manufactured and sold today.
Old and New Jacobs Super Chuck (16N) Components — Jaws, Ball Bearings, and Split Ring
Jaws
Split Ring
Ball Bearings
First there are three independent jaws 1-2-3, threaded on one side of one end, and ground to angles on the other. They are hardened for long service life — they are literally the hard parts.
By the time your chuck is first assembled the split nut will already be in two pieces. This intentionally broken piece is the ingenious core to Jacobs' design and fulfills the key design requirements: engage with the jaws, engage with the outer, and fit over the central core. The bottom end of the jaws is threaded so that they can advance and retract in unison and the split nut has the mating threads for that motion. To fit around all three jaws, and the body of the chuck, the nut has to be split in half so it can come together around the jaws.
Manufacturing Tip:
Brittle materials will break and keep their shape so they can be put back together and "register", keeping their original relative dimensions intact. This means the threading inside the nut still works, even though the piece was split into two!
Finally, the sleeve presses on to the split nut and holds everything together. The press-fit also means that when the sleeve (on the outside of the chuck) turns, so does the split nut, moving all three jaws simultaneously.
Manufacturing most parts is difficult enough, but making a complicated threaded part, ground to the perfect size for the interference fit, then broken in half is unusual. A better description of the design is creative, there is no other way to assemble the chuck unless the split nut can come apart in two pieces.
Ball Bearings allow the split nut to spin smoothly while tightening or loosening
Jacobs Super Chucks are built with commonly found ball bearings, making replacements easily findable. The bearings usually don't see much wear since the split nut rides on ball bearings only when tightening or loosening. When the chuck and bit are drilling a hole, the balls are stationary in their positions within the chuck- they do not roll.
Chuck | Ball Bearing Diameter |
8 1/2N |
1/8" |
11N |
5/32" |
14N |
3/16" |
16N |
3/16" |
18N |
7/32" |
20N |
1/4" |
By most historical accounts, Arthur was not highly educated. But he must have been very observant, and had acquired some experience and knowledge to enable him to make such a creative and useful design. The design skills include machining, threading, geometry, gearing, fits and tapers. Metallurgy is usually used to design parts that do not break and have the correct hardness and other qualities for the mechanism-glad he skipped those classes.
The chuck also embodies a very important design philosophy, elegant and simple is usually hard to achieve, but he did it.
Drawings from Jacobs' original 1902 patent
Jacob's first patented his Super Chuck in 1902. After some very minor improvements he again applied for a patent in 1912. The drawings show the sleeve with a diamond knurl pattern while the many older style Jacobs Super Chucks with straight sleeve splines mechanically identical. Some minor aesthetic changes have occurred over time, but the original (nearly 120-year old) idea from 1902 has proven to be a great one.
To truly experience Jacobs design, we recommend taking the time and disassembling one. It's also a great time to perform some preventative maintenance and give some life and lubrication to an often neglected piece of shop equipment.
Get a service ring and press the sleeve off the arbor with an arbor press. Fully remove the sleeve over a lunch tray and take it all apart. Check out our video of the whole process. Shops are dirty and over time, lack of lubrication coupled with a buildup of sawdust or metal chips can bring your chuck to a halt. All the parts are available to make it new, all of our videos are there to help with the most common repair problems. This is a great project for an apprentice to learn and at the same time improve your shop's productivity and performance.
We've built up a bit of a collection — I think you could say we're fans.
Modern Super Chucks still have the same operation as the original 1902 design
Splitting a hard nut in half was the key to the Super Chuck's assembly
A little love goes a long way to keep chucks working for decades
Andrew Prestridge | September 12, 2020
Screws are defined by three measurements: diameter, pitch, and length. The diameter is the distance across the threads (how "fat" the screw is), length is how long the screw is, and pitch is the spacing between the threads. Screw length normally does not include the head, except for flat-head screws. For the pitch, you can either measure the distance between threads, or measure a fixed length of threads and count the number of threads in that length.
A good example is a 1/4"-20 x 1" screw. This screw would have a diameter of about 1/4", have 20 teeth per inch of threads, and be 1" long (plus the height of the head.) Since it has 20 threads per inch, and is 1 inch, we would expect there to be a total of 20 threads on the screw.
A thread gauge measures the number of threads per inch (here 40 TPI)
Zooming in shows how well the gauge matches the threads on the part
A metric example would be an M12x1.0 x 25mm. This screw would have a diameter of about 12mm, have a distance of 1.0mm between each thread, and be 25mm long. Since there is 1.0mm between each thread, and it's 25mm long, we would expect there to be a total of 25 threads on the screw.
However, this naming convention gets a little trickier for small imperial screws. Below 1/8" imperial screws use a number system (ranging from #12 to #0000, super tiny). Smaller numbers here mean a smaller diameter, so a #4 is smaller than #8. As screws got even smaller, they just started added zeroes, so a #00 is smaller than #0, and #0000 is even smaller still.
A common small imperial screw is the #6-32x1/2” which means a #6 screw (which has major diameter of 0.138”), with 32 Threads Per Inch (TPI), that is 1/2” long. There are multiple methods of measuring pitch, and sometimes a thread pitch gage is the quickest method; we also have a lead angle calculator for screws and threads.
The Threads Per Inch (TPI) is the number of threads along one inch of the length of the screw, just as the name suggests. By simply counting the number of threads and dividing by the length you can easily calculate the TPI of a screw.
Metric screws convey the same information, but with slightly different terminology: the second number is the length between threads, not the threads per inch. For instance, an M6x1x20 screw has a diameter of 6mm (M6 means Metric, not a #6 imperial), a pitch of 1mm and length of 20mm. The pitch of 1 doesn’t mean that the screw has only 1 thread per inch, but rather that each thread is spaced apart by 1 mm. Since there are 25.4 millimeters in 1 inch, the M6x1.00 screw has an equivalent TPI of 25.4.
As the TPI increases for screws it means there are more and more threads in the same one inch, so the threads are getting smaller and smaller: a 6-32 screw has bigger threads than a 6-40 screw. By contrast, in metric screws as the pitch increases the individual threads take up more space and are increasing in size, so an M6x1.00 has smaller threads than an M6x1.50 screw - TPI and pitch are inversely proportional.
For good or for bad, there hasn't been a Whitworth-esque standardization movement for gears.
This same relationship holds for gears, the imperial dimension is Diametral Pitch and the metric dimension is called Module. The Diametral Pitch is the number of teeth of a gear per inch of its pitch diameter (effectively the same as a screw’s TPI), while Module is more directly the pitch of the gear. Just like in screws, a gear with a Module of 1 has an equivalent Diametral Pitch of 25.4. As the Module increases, gear teeth increase in size, but as Diametral Pitch increases those gear teeth decrease in size in order to fit more teeth into the same inch of pitch diameter. If you ever need to convert, just use the following equations:
Diametral Pitch = 25.4 / Module
Module = 25.4 / Diametral Pitch
Figure from "A Treatise on Gear Wheels" by George Grant, 11th Edition, (Figure 31 graphical comparison of gear pitch - with edits) 1906
Measure the major diameter across the threads. Higher is larger is both inch and metric screws
Inch screws count the Threads Per Inch, while metric screws measure the length between threads
Measure the length beneath the head of the screw, except flat-heads measure the whole length