Marshall Johnson wrote:

jim rozen wrote in message ...



Post up the sfpm you were running on the tool,
and the feed rate. Either your idea of 'slow'
for the rpm is incorrect, or you were running
the feed rate so slow as to allow the material
to work harden under the tool.




Sorry for the late reply.

The spindle speed was 200 rpm. Originally the feed rate was 1.5" per
minute, but that was when we wrote the program for the mild steel. By
the time we were taking a good cut into the metal, we had the feed
rate slowed down to about 1/10" an inch per minute.


Well, there's your problem! With any material that work hardens (SS is
notorious for this, but many other harder materials also do it) you reduce
the depth of cut, and may need to INCREASE the feedrate!
There's no way you can make this cut in a single pass except with monster
machines and very large diameter cutters.

(A horizontal mill could do it in one pass if rigid enough, but due to
the nature
of the cutting action, a vertical mill ends up producing very thin chips
at the
sides when plowing at full width, and this is where the work hardening
begins to develop.)

Jon

Keep in mind that we were trying to cut through this 1/2" piece in one
pass. It looks like we're going to have to bump up the feed rate and
only go half way through the piece on each pass, or maybe even less.