Jacobs chuck

[Gordon]

I have two Jacobs ball bearing chucks which I inhered from my dad. They are a 16N and 3A and both appear to be almost new and in good shape. They both have about .010 total runout (+/- .005 per side). I have checked the mounting spindle and that checks out OK. The problem is in the horizontal direction not the vertical direction. New jaws are available but are quite expensive given that I do not know if they will fix the problem and the old jaws do not appear to be worn or damaged. Is there some way to determine where the problem may be? I have not disassembled them and I am a little hesitant to do so.

Any advise or ideas?

Gordon

 

[deverett]

First job, if you haven't yet done it would be to ensure the inside of the chuck is completely clean of swarf. I hesitate to recommend it, but in this instance compressed air may be the weapon of choice before soaking it in some something like white spirit. Swarf can sometimes get jammed in the 'works'.

See if that makes any difference.

Dave
The Emerald Isle

 

[kvom]

I assume you're measuring runout on some round bar held close to the jaws. Before doing anything else, measure the body of the chuck as well to ensure that the shank is not cockeyed.

 

[Gordon]

I will do some more investigation on this when I get a chance. There is a good chance that they are actually defective. My dad was in charge of the tool crib at a die shop and if something was replaced because it was defective it is highly unlikely that he would throw it away. He was much more likely to take it home. These are items that he was unlikely to justify purchasing for personal use.