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Lloyd E. Sponenburgh[_3_]

fired this volley in
:

I use my fingers on the OUTSIDE of the part. Not on the bar. That's
why the use of a piece of leather. And then oil on the part. Putting
some sort of vibration dampening at the point of vibration generation
seems to work best.
Eric

The part isn't what's springing. I did my test cuts on a thin ring of
material solidly clamped in the chuck. I can assure you, it did not
contribute to the chatter I got.

"Fingering" the boring bar _did_ reduce the chatter to an almost-
acceptable level, but remember -- I've got a full 15" overhang on the
compound. That's _way_ beyond what's going to work on any lathe smaller
than (perhaps) a 36" swing.

I wasn't going to condemn a good piece of stock that I might use for
other purposes, just to do a test. The test piece was just a small drop
from a prior job.

The best solution is a "drill" made with adjustable followers that track
the surface of the cut as it proceeds. This is similar to the "packed
bit" principle used to bore cannon.

If I find a need to make more of these, I'll probably build a dedicated
boring device that is self-powered, and doesn't rely on my lathe's
rigidity to do the job. It's not complex... just a lot of work.

Lloyd