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wrote:

Peter Fairbrother wrote:
Any hints for turning pure copper?

Like the other guy said, 0 degrees rake, basically a flat top tool.
Any positive rake will hog in, as you've found out. I've turned a lot
of commutators and usually take off about .005" at the most with that
interrupted cut. I haven't had to use any coolant. I use HSS and use
a diamond hone on the tool to polish before using it. Feed slowly and
don't get in a hurry and the finish comes out just fine. A round-nose
tool helps, too. Make sure it's dead on center, too high or low is as
bad as having rake.

Yesss!

I used:

sharp tool steel (HSS+) but no diamond honing, zero rake no breaker
(_actually_ a flat top tool, I just polished up a 15 degree clearance blank
on a fine wheel)

dead on center, fast speed, slow feed, small cut

milk (didn't have any d-limonene) fed on a soft paintbrush to limit mess and
smell when it goes off, the prospect of a suds tank full of rancid milk
didn't appeal

and it works great - lovely surface finish, like a mirror, very little force
used ...

.... and no hoggin, so I feel confident to turn the expensive (they aren't
actually expensive, but they have had a lot of work done on them) work
pieces.

Perhaps a little slow for quantity production, but perfect for my purposes.

Thanks very much all.

--
Peter Fairbrother