Arthur I. Jacobs and his Super Chuck
History of the Super Chuck
In 1900 Arthur had a job to do in the shop; he had to 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.
From large to small, 20N, 18N, 16N, 14N, 11N, 8-1/2N all 6 of the Jacobs Super Chucks
The 4 Moving Parts
Arthur had probably been drilling a lot of holes and thinking about how to do it better for a while, so he set out to improve on the chuck and came up with a 3-Jaw mechanical "Super Chuck". Other than ball bearings in the race, there are only 4 moving parts.
The Three Hard Parts
First there are three independent jaws 1-2-3, threaded on one side of one end, and ground to bit biting angles on the other. They are hardened for long service life. These are literally the hard parts.
One Ingenious Part
But the other part is really an assembly of a two-part split nut pressed inside the sleeve. I can count, these are three parts, but once assembled, they act as one — the sleeve and nut move together. The sleeve by itself is interesting because it has the characteristic tooth and angle of a bevel gear that meshes with the chuck key when tightening. The split-nut inside it is broken on purpose, yes a designed break. When you assemble the sleeve over the nut (which rides in a groove in the arbor) they act as one part. Brittle materials will break in such a way that it can be put back together and "register", keeping their original relative dimensions intact. This means the threading inside the nut still works as designed and machined because it has the same orientation before and after the break.
The nut and sleeve assembly are separate for installation and then installed to a press-fit with a service ring —this same ring can be used to disassemble for maintenance and repair. The press fit holds the entire chuck together and also keeps the split nut "registered" as if it had never been broken. There are no bolts or pins or any other fasteners holding the chuck together.
The Split Nut and the Press-fit
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.
The split nut rides on ball bearings, but only when tightening or loosening. To be clear, the ball bearings are only in service when opening and closing the chuck to insert and clamp on a drill bit shank. When the chuck and bit are drilling a hole, the balls are stationary in their positions within the chuck- they do not roll.
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.
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.
A powerful combination for your shop
The 14N Super Chuck can accept drill shanks as small as 0.040" up to 0.500". Combine it with a bit box (MADE IN USA ONLY Please) that has letter, number and fractional bits within this range. No waste here, you can use every single one of the 115 drill bits in the box. Fit the 14N to your drill press, Bridgeport or lathe with an arbor that is the same for all of them.
Give your 100 year-old Jacob's Super Chuck a new life
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.
Our favorite is the older style keyed Super Chuck with a straight splined sleeve pattern used with a Morse Taper 3 or 4 arbor.
© Evolvent Design, 2020