This thread has been interesting for the number of posters who have
lathes with modest high speeds and who don't feel it's a problem.

I have a 10 x 24 Jet with a max speed of 2200 rpm +-. I have a
controller for it that takes the FPM desired and the diam, and drives
the VFD to give the right speed. I often find the the controller wants
the spindle to go faster than 2200. In ordinary circumstances, e.g.,
mild steel & 1/2" diam. Such that I was considering re-pulleying it to
get higher speeds (if the spindle bearings would be OK with it).

My assumption has been that the FPM is not just a matter of efficiency
(i.e., production speed), but of surface finish. That too low FPM will
produce a worse finish than a higher "right" value. Am I wrong? Is FPM
just a max value to keep production up without destroying the tool?

As always I'm sure that the vast collective knowledge here will have the
answer,
Bob

On Wed, 10 Feb 2010 11:48:24 -0500, Bob Engelhardt
wrote:

This thread has been interesting for the number of posters who have
lathes with modest high speeds and who don't feel it's a problem.

I have a 10 x 24 Jet with a max speed of 2200 rpm +-. I have a
controller for it that takes the FPM desired and the diam, and drives
the VFD to give the right speed. I often find the the controller wants
the spindle to go faster than 2200. In ordinary circumstances, e.g.,
mild steel & 1/2" diam. Such that I was considering re-pulleying it to
get higher speeds (if the spindle bearings would be OK with it).

My assumption has been that the FPM is not just a matter of efficiency
(i.e., production speed), but of surface finish. That too low FPM will
produce a worse finish than a higher "right" value. Am I wrong? Is FPM
just a max value to keep production up without destroying the tool?

As always I'm sure that the vast collective knowledge here will have the
answer,
Bob

I've found that carbide produces a better finish at higher speeds, but
I get good finish with HSS at any speed. Last week I made a pin with
0.100" dia running at 640 RPM, this to repair a toy for the little boy
next door.