work slipping in 3 jaw chuck

awander said:
You probably mean tightening all 3 pinions one after the other, right? There is no way to tighten the jaws individually on a scroll chuck.
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Thats right, just to rule out a possible problem.
 
Tony's suggestion to lube the scroll is a good one. It can't tighten much if there is a lot of friction. I have never had a problem with a chuck not holding.

IF I DID,I'd recommend wrapping a strip of brown(no clay in it) paper around the work piece. Paper will hold like crazy in a chuck,a vise,under a tool post. Try it.
 
Are the jaws in the correct slots (number on jaws match the number on slot)? They could be in the correct order but shifted off by a slot....couldn't this allow a jaw to have lateral movement in an unmatched slot resulting in the part becoming loose. Just a thought..........
 
Thank you for all your "comments". The chuck is about 6 months old and has never had the jaws removed. The 3 jaws tighten as one unit when any one of the 3 tightening positions. I have the chuck taken off the lathe and it is setting on a bench. I have removed the screws from the back and the chuck has a slight line about 3/8' from the back. No matter what I do, I cannot separate it into 2 pieces. I am also afraid that if I manage to separate the 2 portions, I might not be able to get it together again. (too much runout) Is there a way to clean the chuck without dis-assembling the thing. I live in a small town in the south and I have no person that is a machinist to answer my questions. That is why I appreciate Ya'll.
 
Put those screws back in, but leave the heads standing proud a little and drop the chuck straight down on the back on a wood tabletop or piece of wood on top of something pretty solid. If the mounting studs are in the way, remove the backing plate so that the heads of the screws are the only thing protruding from the back of the chuck. If this isn't practical, leave the screw heads proud and take a deadbow mallet or something comparable to tap them, separating the chuck halves. Usually, once you get a separation started, it's not tight all the way. Just be careful to make sure there is enough thread engagement to take the force of the blows. In other words, once you tap the screws back down into their counterbores, you can back them out a little more and go at it again, but if there are only a couple of threads engaged you can't hit the screws very hard without risking damaging the threads. You could get some longer screws, and that might get you more room to work at it this way. You also need to make sure you keep things even. Don't just beat on one of the screws.....go around the bolt circle evenly. A tap or two on each screw at a time.

Also a good idea to make a match-mark the halves to make sure you get it back together as it was when new.
 
Pmedic828 said:
Thank you for all your "comments". The chuck is about 6 months old and has never had the jaws removed. The 3 jaws tighten as one unit when any one of the 3 tightening positions. I have the chuck taken off the lathe and it is setting on a bench. I have removed the screws from the back and the chuck has a slight line about 3/8' from the back. No matter what I do, I cannot separate it into 2 pieces. I am also afraid that if I manage to separate the 2 portions, I might not be able to get it together again. (too much runout) Is there a way to clean the chuck without dis-assembling the thing. I live in a small town in the south and I have no person that is a machinist to answer my questions. That is why I appreciate Ya'll.
Click to expand...

Here's a pic of a 3 jaw taken apart from this thread.


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