Debur Internal Taper On A Jacobs Drill Chuck?

In this case "many cooks improve the broth" Working together we've come up with a superior method of repair, probably the easiest and most fool proof method of repairing a damaged internal taper.
 
I did it as Bob described, except I used a dowell in the 16n and a collet in lathe ,
Tryed it with a 1-1/2" reduced shank drill in 1/4" plate , no pilot hole , worked good
 
John C said:
Thanks Doc, I'll give that a try.

About securing the chuck in the lathe. I could strip it down and secure the OD of the chuck body in the 4 jaw, or leave it intact and tighten it down on a 1/2" ground rod secured in a collet...... Hmmmmm..... There is virtually no wear on the bearing surfaces of the drill chuck jaws. I don't know how true the OD of the chuck runs in relation to the jaws...... Any thoughts? I'm leaning towards clamping the chuck on a ground rod mounted in a a collet...
Click to expand...

This is an interesting idea. But instead of using a collet, the ground rod could be zeroed in a 4 jaw then the chuck mounted on the rod. The run out of the taper could also be checked with a DTI and high spots located accurately. Then the choice of tool to remove the high spots might be more obvious. I agree about leaving any other part of the original taper untouched.

I can't see you doing a good job without a DTI. If you have too much run out either with a collet or 4 jaw, I would tighten the chuck on a long rod and use the same approach as when chambering a barrel through the headstock so you can dial run out of the taper to zero.
 
Last edited:
Sorry for the delay in replying. I went ahead and turned a piece of copper rod for lapping. (The burr was around the full circumference of the chuck, I don't think I could have done it with a stone.) Anyway, I set the taper attachment to 0.0635" over 2" of travel. (Be aware that littlemachineshop.com has a typo in their taper tables for the 33JT taper). With the copper lap mounted in a collet, I mounted the workpiece on a short length of 1/2" ground rod in a chuck in the tailstock. Working in back gear I lapped the chuck starting with valve grinding comp., and then some much finer compound. Re-dressed the lap a couple times along the way. I counter-rotated the work in the tailstock by hand as I lapped.

Well, now I've got a chuck that mounts nice and tight on the drill press, but it still has way too much run out when chucking a test rod or bit. Thinking maybe the body of the chuck is bent? Took the chuck apart, and the split nut and jaws look very good. When re-assembling, with just the chuck body, jaws and split nuts held together by hand - the split nut has LOTS of room to "orbit" around the threaded portion of the jaws. I understand there needs to be clearance, but it seemed excessive. I'm wondering if someone had rebuilt the chuck with the wrong kit at some time? The chuck is a Jacobs 34-33C 0-1/2".

Is anyone aware of Jacobs rebuild kits for different chucks that are close, but not quite right?
 
I think I may have just answered my own question........ Maybe the nut is installed one tooth too low on each of the jaws.......
 
Last edited:
I agree with Tony(and any others who offered similar advice). I would NOT lap the whole #33 hole. It will probably mess up the concentric running of the chuck. Also,might cause the male taper to hit bottom and still be loose on the chuck. Just take a SMALL wheel on a Dremel and grind a shallow groove around the inside ONLY where the burring occurred. Best to leave as much of the original,untouched taper there as possible.
 
The lapping worked out just fine. Quite well in fact. The body of the chuck was bent. No solution to that which wouldn't have required more effort than it was worth. Found another chuck that runs .003-.004 runout 3" from the jaws. I can live with that.

Some times you reach a point of diminishing returns.....
 
John, thanks for sharing your experience with us.
 
You must log in or register to reply here.
Back
Top