Thanks Randy. I think I'm going to send an email to Jacobs and see what they say.
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Problem Rebuilding Jacobs Chuck - Suggestions?
- Thread starter Nogoingback
- Start date
did you try sliding the 2 good jaws into the bad hole or slide the bad jaw into the other 2 holes this will confirm that the larger jaw is in fact bad and not the hole. otherwise I would try to polish the slightly larger down till it fits if we are talking about chuck run out do you know how much run out was initially with this chuck. I don't think you will put the chuck out of normal range. of course this all depends on how much slightly over it is. slightly over is not really a machinist term. maybe less than .001" bill
The #1 and #3 jaws slide into all three bores, while the #2 sticks in any of the bores, though one of the bores seems slightly smaller. (Haven't measured them). I don't have the numbers in front of me, but the #1 and #3 jaws measure
the same diamer, while the #2 jaw measures .0005 larger. This suggests to me that the problem is the jaw, not the chuck body.
Naturally, I have no idea how Jacobs toleranced these parts, so I don't know if that puts the #2 jaw out of range.
As for run out, I have no idea what it was before: I bought this chuck on eBay for a lathe I'm refurbishing, so I've never used it.
the same diamer, while the #2 jaw measures .0005 larger. This suggests to me that the problem is the jaw, not the chuck body.
Naturally, I have no idea how Jacobs toleranced these parts, so I don't know if that puts the #2 jaw out of range.
As for run out, I have no idea what it was before: I bought this chuck on eBay for a lathe I'm refurbishing, so I've never used it.
so at .oo05" I would polish the bad jaw until it just fits might only take .00025 to get it to fit and at that number runout will be minimal at best. at least you will have a chuck to use with no additional cost. you might have got a hole at the very least of its tolerance and a jaw at the very most of its could happen. I repeat polish it until it just fits bill
My wife bought me a small drill press 25 years ago, a Delta 8". Useless because of size. But more useless because the Jacobs chuck had one jaw that was no true. So bits wobbled. I may send that back so I can sell the damn thing. I find it odd when everyone says how good we used to build things in the US. Certainly we COULD build some really good stuff, but we also lost that ability and were still making it here, and it was no better than China.
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]Sometimes, the jaw will go in if turned 90 degrees from normal and go in. If you can get it to do just that, twist the jaw several times to get a dull spot in the ID of the chuck body. This would indicate positive metal that needs to be removed. Now it the jaw will not go at all turned 90 degree, then it could be the jaw. I have polished the jaws too to get them to go in.
as far as I know there is not a numbered hole just the jaws and thread part so fit the biggest jaw into the largest hole and set the jaw sequence from there but I may be wrong about this been a long time since I rebuilt one of these. bill
Now that I think of it, I can turn the jaw 90 degrees into the bore. I'm out of town, but when I get home I'll have another look with that in mind.