Jacobs Ball Bearing Chuck Rebuild (14N) Done My Way

tool post.jpg chuck.jpg jacobs.jpg No problem separating the chuck from the arbor, but I decided to try to improve the runout which was close to 0.007". Fail. I trued up a piece of 3/8" drill rod in the lathe chuck and placed the jaws of the drill chuck (No. 11N) over the drill rod and clamped. Having previously set the taper, I ground the Jacobs taper. Now the chuck has a noticeable wobble and has about 0.012" runout. I won't try that again. If someone needs an 11N with a brand new full kit installed, but with a junk body, let me know.
 
I can't see that set up with a Dremel improving accuracy on a taper. The Jacobs taper on the body is
very precisely ground. That 11n is now a paper weight, sorry. You can sell the parts and throw the body away.
The jaws and half nuts must be matched and if the thrust race and ball bearings are good, sell those too. Maybe a package deal
for someone with an old 11n that needs a refurb.
 
Why not just chuck the largest accurate round and skim the shank after installing it in the bad JT? If you can use a straight shank this is pretty simple. Use a carefully drilled center hole and a good ball bearing center when turning. I have trued up bent straight arbors in this manner with acceptable success.
 
You're better off just finding a good drill chuck. Lot's of good USA Jacobs still floating around.
Rohm chucks are very nice also. That 11n will never be the same. Chuck bodies are not hardened and are
susceptible. The jaw holes are very precise. They just weren't built to last unless you take very good care of them.
Good luck.
 
EmilioG said:
Just out of curiosity, did the 14n with excessive run out that you mentioned, was that the one with the shorter
chuck body jaw hole part? I've never seen a Jacobs like that with such a short body where the jaw holes end.
Click to expand...

No, that one that was different from the other was actually the nicest of the 3 & the one with the lowest IIRC. The one with excessive runout had .006" TIR due to worn/damaged jaws (it was the worse condition one of the 3). I replaced the jaws & TIR is now just under .003". Still within spec but not as great as my other 2 which have .002" TIR with no replacement parts needed.
 
I didn't show the interior taper in body of the Jacobs 11N before I tried cleaning it up. This chuck came from a municipal garage that had Neanderthals for mechanics. It looked as if someone had taken a 4 pound blacksmith's hammer to remove the chuck from the machine spindle; the rings of Saturn were visible in the internal taper. This was just an attempt to see if I could correct some of the damage. I think I would have been a lot better off chucking the body of the Jacobs chuck rather than using the jaws. I like the idea of turning up a "dedicated" spindle for the chuck.

(P.S. - I made a new spindle for the little Buffalo drill press and a new drive pulley. The little machine is a 14" that was made before WWII and is a sweet running little machine. That was after I brazed up a long crack in the head of the machine that was caused by some extreme over tightening by the same crew of thugs)
Geoff
 
In regards to the 11n being talked about, it's not total junk. It can be fixed given the correct tooling & setup. Whether or not it's worth fixing depends on what tooling the user has available.
 
darkzero said:
No, that one that was different from the other was actually the nicest of the 3 & the one with the lowest IIRC. The one with excessive runout had .006" TIR due to worn/damaged jaws (it was the worse condition one of the 3). I replaced the jaws & TIR is now just under .003". Still within spec but not as great as my other 2 which have .002" TIR with no replacement parts needed.
Click to expand...

Are you checking TIR at half capacity? 6 - 6.5mm ? Have you checked it at different capacities?
 
EmilioG said:
Are you checking TIR at half capacity? 6 - 6.5mm ? Have you checked it at different capacities?
Click to expand...
6mm what, there goes that foreign language again. ;) I checked them with a .400" gage pin. They're just drill chucks & not one of my lathe chucks or collet chucks. That's good enough & not as important to me.
 
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