Hard Jaws Not Clamping Square on Material

[racecraft]

I have a SL-20 with a 8" 3-jaw Samchully chuck. I purchased a set of serrated hard jaws. They are pie jaws so they dont come to a point in the center. The jaws are about 2" deep.

When i am attempting to turn a smaller (.375"-1.00") piece of material with less chuck pressure, the jaws are not biting into the material as much toward the positive side of the chuck as they are toward the negative side. Sometimes they dont even touch on the end of the jaws.

This is resulting in chatter issues when turning. I have used a tailstock with a live center. That helps but still does not make it perfect. As we all know, many times a center can not be run.

I know the jaws "float", but is there some kind of adjustment that i need to do in the chuck?

My other thought was to see if there were such things as a serrated hard jaw that is only 1" deep. This still isnt fixing the mis-alignment problem but would solve the chatter issue. If anyone knows where i could get a good set of those would maybe help to.

Any ideas or am i just S-O-L??

Thanks, Racecraft

[Geof]

That is the problem with hard jaws; any little bit of play from wear or distortion lets the jaws splay open at the front.

I guess these are removable jaws?

A bit of a hokey fix, which does work, is to slacken the jaws and put some small pads of shim stock between the jaw and the jaw base at the outer end; this tilts the tip of the jaws inwards.

It also means the jaws are only contacting the base at each end with something of a gap in between so reefing the bolts really tight may not be a good idea and using the jaws at very high clamping pressure may not be wise, but for low pressure clamping on small parts it is okay.