Soft Chuck Jaws vs Hard Chuck Jaws

[ranparn]

We manufacture chrome plated steel rods and tubes and turn them on a lathe. The tubes are 1026 and the rods are usually 1045 steel. We've been having trouble with machining chips getting embedded in the chuck jaws creating dents and dings on the outside diameter of the tubes. These tubes are not induction hardened so the hardness of the surface is around 26 HRC. My plant wanted to try brass jaws or aluminum. Seems to me that would be worse for getting chips embedded in the jaws. I suggested getting a set of case hardened chuck jaws that would be harder than the steel you are machining that way there would no chance of chips getting embedded, they would just fall out. Need thoughts on this...

 

[IRstuff]

Scrub brush?

TTFN
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Need help writing a question or understanding a reply? forum1529

Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

 

[racookpe1978]

You've got to look at the clamping (and chip cleaning) process, not at the hardness only of the jaw.

See, your current work (the steel being turned) is being damaged by chips (from the previous piece right ?) being trapped between the new work piece and the jaw clamps. A chip produced from the current work being turned can't get trapped between jaw and work.

The chips are as hard as the steel being turned because they come from the steel being turned. Kind of trite to remember that, but does it mean the only way not to damage a work by chips is to use such a soft jaw that the chip is embedded in the jaw completely? There the embedded remains, to possibly damage every future piece clamped by the jaw? After all, the third chip getting trapped by the same set of jaws is going to be trapped between the first and second chip and the fourth piece of steel ... and on and on.

Your jaws have a very limited contact area between jaw and workpiece.

That limited area is going to continue trapping chips until you find a better way to clean the jaw before clamping a new piece of steel. A

 

[Compositepro]

Cleanliness is an essential aspect of machining. I hope they clean the mounting surfaces of the chuck onto the lathe better than what you are describing. The is part of learning to be a machine operator. I think you have a training issue.

 

[tbuelna]

The only solution to this problem is keeping chips out of the chuck. The most obvious approach is to teach your lathe operators to take the time to thoroughly clean the chuck before fixturing the next part. Remind them that they are not being paid by the total number of parts they machine, but by the number of parts that pass QA.

Another thing that might be helpful would be to install a shield over the chuck, and maybe also pump some compressed air through it, to reduce the amount of chips that find their way into the chuck.

If there are metal chips trapped between the rod surface and the chuck jaws, it will make no difference in how hard the jaws are. Either aluminum or steel jaws will create enough clamping pressure to produce surface damage on the rod if a metal chip is trapped between them.