Chatter when facing pipe

[PMartin]

I was making some spacers out of some pieces of 3/4" pipe. I cut them just a bit oversize in length, then chucked them up in the lathe to face off and chamfer the ends while getting them to the correct length. While facing or cutting the chamfer I kept getting a LOT of tool chatter. I had never had this problem before so I chucked up a piece of 1" solid stock and faced and chamfered one end of it without any chatter whatsoever.

Any idea why I get chatter on the pieces of pipe but not on solid stock?

 

[P. Waller]

Material difference.
The pipe is produced from sheet stock roll formed then welded, the material can be considerably different then common wrought solid forms.
Cold working during the forming process will also alter the characteristics.

 

[mikey]

Just curious how you cut the pipe. Some of this stuff has enough carbon to get harder if you cut it with an abrasive blade. I've faced Schedule 80 once and had to slow the lathe down a bit to cut it and I used brazed carbide to do it. You might give that a try.

 

[derf]

Pipe is not exactly round and your chuck is probably not getting a good grip on it.

 

[Bob Korves]

Pipe is not exactly round and your chuck is probably not getting a good grip on it.

Pipe is not often perfectly straight along it's length, either. Also, if you have a nipple that has been threaded on both ends, the pressures involved can make the whole thing barrel shaped beyond the tapers themselves. Does not make for simple chucking on a lathe like a piece of cold rolled...

 

[FOMOGO]

All of above + being a tube it will more easily produce nasty harmonics/resonance. Maybe read through this info http://timbobtastic.com/hints-and-tips/avoiding-chatter/ . Mike

 

[Road_Clam]

A pic of your chamfer method setup would be helpful. I worked machining weld prepping "black pipe" for many years. Black pipe can get tricky to machine in certain circumstances from vibration chatter especially the common schedule 40 (thinnest wall). Schedule 80 (thicker) gets a bit easier. Black pipe is soft and can "grab" your tools. slow rpm's, light cuts and some cutting oil. Don't stick the stock too far out of the chuck.

 

[PMartin]

Thanks for the replies everyone. I think you all bring up some good points. Just for curiosity I took a couple of untouched pieces over to a friend and we tried it in his lathe, first in a three jaw chuck and got similar chatter. Then he put on his four jaw chuck and dialed in a piece of pipe and tried that. It still had some very fine chatter marks, but not nearly as bad as when using the three jaw. He figures that pipe is a bit flexible since it is not very thick. The four jaw chuck gives it better support. We think that a six jaw would have worked pretty good, but we don't have one.