chatter again, again, again........

[Loose nut]

I am in the middle of turning a #5 Morse taper sleeve out of 416 SS, using the tailstock offset method, and when I started I had some bad chatter.

After playing with the speed it settled down to a nice chatter free matte finish. After a couple of passes the chatter started up again but as I got closer to the headstock end (large end) the chatter stopped. On each pass the part of the taper that is chattering gets shorter and shorter (closer to the small end) and should be completely gone before it is turned to the right OD.

Any ideas what causes this??

 

[jthulin]

No experience with type 416, but I have had to deal with various pieces of "scrap" that had difficult sections along the length. Could the material be work hardened at the nasty end? As you progress, less and less affected material remains? Just a thought. Try increasing the feed rate. Seems to be the wrong thing to do, but gives a higher load on the tool edge which reduces vibration. Good luck scratch.gif

 

[kvom]

The large end has a greater SFM than the small end.

 

[websterz]

The large end has a greater SFM than the small end.

Yep, it's the same effect you see when facing a large diameter piece. The finish on the outer portion will be nice and smooth then it starts to degrade as you approach the center. That's why on a CNC lathe the RPM's increase as the tool nears the center.