Rebuilding A Jacobs Chuck

Modified on 2015/12/01 10:37 by Jeff Joslin — Categorized as: Drill Presses, Maintenance

From owwm.org forum essay by John Grieser

See also owwm.org essay by Bill Nance with some useful suggestions by others.

This is intended not so much as a tutorial of any sort, but more as documentation of what I did, and as a "if I can do it, anyone can do it" sort of thing.

More information about drill chuck repair can be found at:

- Beautiful Iron

- Jacobs Chuck Technical Support site

- The Drill Presses section of the OWWM Wiki

This shows the disassembly and reassembly of a Jacobs 6A 33 chuck. I do have a small arbor press, but the only additional piece I needed to purchase was a 69 cent piece of PVC from the plumbing dept at Home Depot.

I extended the jaws of the chuck before pressing the sleeve off. Some sources say to extend the jaws half way. You may need to experiment with your chuck to find the best jaw position. Before disassembly, make sure that you can keep track of the orientation of jaws to chuck - they need to go back in the same order to allow the split nut to align the jaws properly.

The main body of the MC chuck is 1 5/8", a perfect fit for the smaller diameter of the plumbing piece (shown later) to support the sleeve while the body is pressed out. This photo shows a scrap of particle board with a slightly larger hole to support the slightly larger body (and sleeve) of the 6A.

It takes a bit of pressure to pop the sleeve off, but you'll know it when it comes loose.

Sleeve removed:

Threaded rings (or split nut) removed:

Jaws removed. Everything ready for some TLC:

After soaking in lacquer thinner and wire brushing. I also scrubbed with an old Scotch-brite pad and an old tooth brush:

Applied grease to jaws & threaded rings and re-assembled:

Make sure that the jaws are all inserted equally into the chuck body. It takes a little fiddling to get the rings seated perfectly.

Sleeve placed onto re-assembled chuck, ready to be tapped in place with a hammer:

One of the sites I consulted warned against pressing the sleeve back on, saying that it could produce too much pressure and distort the body of the chuck.

(Note: This may be in reference to Beautiful Iron's warning about not pressing the chuck onto the taper/arbor of the drill press. It should be safe to press the sleeve back onto the chuck using typical precautions and reasonable force.)

Chuck reversed in the jig, ready for tapping:

69 cent plumbing jig can also be used:

It took about 5 good raps with a hammer to seat the sleeve:

Finished chuck:

I was amazed at how easy this process was, and how great the results were. It only took about 30 minutes and was very high on the satisfaction scale.

Here is the 6A next to the MC-33 I did yesterday:

Thanks for looking. Hopefully I didn't leave anything out.