PDA

View Full Version : Reversible jaw chuck question



chip's
05-01-2009, 11:45 PM
I'm sure this is old hat to most of you but I just got an old 8" cushman 3 jaw reversible jaw chuck for my lathe. The question I have is, how much should the jaws move side to side. It looked fine when I got it. When I got all the hard grease and junk cleaned off, the jaws seem loose to me. All the other chucks for the machine have two sets of jaws and almost no side to side movement. Because I didn't have one of these types of chucks before, I don't know what amount of play is normal for a chuck of this type being used as it is. 3 jaws have run out anyway, so maybe this is normal and ok but my 10" with 2 sets of jaws is much tighter. I would be grateful for any information, thanks.

kmccubbin
05-02-2009, 12:17 AM
Sounds like it's worn or abused. There's no reason for the 2 piece jaws to be any less tight than reversible jaws. It's your call whether it's just worn, or worn out.

Kerry

Paul Alciatore
05-02-2009, 01:27 AM
I totally agree with Kerry, the fact that they are reversable has nothing to do with the fit. They are either worn or were of poor quality to begin with.

chip's
05-03-2009, 05:41 PM
Thanks for the input. I was just not sure if this was a normal fit. The chuck has run out of about .008" max. I didn't think was too bad but the side to side play still bothers me. The jaws need help as well, two of the jaws are worse than the other for side to side play. The fixed part of all three jaws comes into contact with the work piece before the changeable part does. Short of grinding I don't see a way around this problem.

ahidley
05-04-2009, 08:15 AM
Why does it matter? If you put in a round part and chuck it up and check for trueness with a dial indicator and it is true within a few thousandths your golden.

Scishopguy
05-04-2009, 10:42 AM
The master jaws contacting the part before the top jaws is not a big issue as you can buy replacement top jaws. The fact that there is side to side movement worries me more. At this point I would be hesitant to invest much in a chuck that has a lot of wear. On the other hand, you could make a set of aluminum soft jaws that you can customize to the parts you turn the most. If you do a lot of thin discs or bushings, you can make them so that those operations are more stable than a normal set of hard jaws.

Just my $0.02 worth.

chip's
05-05-2009, 12:41 AM
Thanks again everyone. The max. side to side slop is about .005-.008 at the center. This does bother me more than the jaws not contacting the work. I believe before I got it,this chuck was used mostly with the jaws reversed to grip large work. The closer to center the jaws go the looser or more slop they have, they are not too bad toward the outer diameter. This is why I believe it was used only for outside work at the end.