Lathe Machining of Delrin

[Ischgl99]

Your steady rest is not concentric with the chuck, it is wobbling it back and forth and drawing it out as it rotates. I’ve had that happen to me before.

Do what rwm posted above, that should solve your problem. You might need to turn a section of the delrin where the steady will run to make sure it is round, if the delrin is oval for example, it might cause the same issue.

 

[WobblyHand]

Why not cut off a 7/8" long piece and turn that? Likely it will make your life a whole lot easier. Yes, you could do what you are doing (once you fix the problem) but why make it hard for yourself?

 

[btvarner]

OK thanks! Let me try these things. Have to wait for tomorrow now. Will report back.

 

[woodchucker]

About 1 1/2". Total length is about 6", but I am using a Center Rest....

A center rest? Do you mean a steady rest? Could it be pulling the stock out. If you have bearing fingers they may be mis aligned.
I would recommend putting a piece of sandpaper around the delrin where the jaws grab. They may give you a better grip.

 

[Charles scozzari]

that makes sense as a possibility. Maybe I need to try a much shorter piece. I am trying not to waist the material as each item I am making is only about 3/4" in length. A 12" lathe is small enough that 2" stock will not got through the chucks or spindle....

Delrin is way too expensive to waste in todays market Try cutting from behind. I believe your using a follower not a steady rest.

 

[Ulma Doctor]

There is the possibility of bell mouthed jaws or a worn chuck.

 

[Charles scozzari]

There is the possibility of bell mouthed jaws or a worn chuck.

In retrospect I think you got it. I just thought there would be visible makings on the Delrin threading on either the surface at the jaws or in the area at the follower. There's rings on the Delrin that suggest that one of the rollers on the follower is bottomed out and the holder is scoring the work.

 

[rwm]

He tried two different chucks.
If the steady rest (it's not a follower) is not centered to the spindle axis it will pull the stock out. As me how I know...

 

[GT-6 Racer]

I expect the steady is not aligned as previously mentioned. An easy way to set the steady is to dial in the part without the steady. Center drill and apply the tailstock with a center. Set the steady rest. Then clear the tailstock. If you don’t need the center drill and don’t want to face off the material, flip the part and work the undrilled end.

 

[benmychree]

Obviously the steady rest is out of line.