This reminded me of a problem I got doing some pieces at a evening class
in Wichita about 1981. Whenever you took a cut on the outside of the
piece you always ended up with what looked like scratches running
parallel to the axis of the piece. The lecturers hadn't seen it before
and they were time served machinists, it turned out to be inclusions in
the round HRS bar which had been drawn out in the rolling process. Crap
bar I guess, I had not seen this problem again until a couple of weeks
ago when I was grinding some HRS angle, it showed the same symptoms.

Jim Stewart wrote:

I'm turning 2 flywheels for a working model
IC engine and I've not been able to get the
quality of finish that I'd like.

The flywheels are about 1" thick and 4" in
diameter. I was working on the face of one
last night. The problem is the small digs
the cutting tool occasionally makes. I can
polish out the overall surface to a mirror
finish with successively finer grades of
sandpaper, but I cannot remove the digs with
the coarsest grade of sandpaper I have.

Can anyone suggest a tool shape and feed that
might give me a better finish. My tool is
slightly rounded with the recommmended angles
for steel.