On Fri, 13 Feb 2015 07:26:30 -0500, "Jim Wilkins"
wrote:

"robobass" wrote in message
...
I'm new to high speed machining. I'm cutting a brass part
http://i1262.photobucket.com/albums/...63/Chatter.jpg
with a 4mm HSS Co TICN cutter. The surfacing works fine, but when I
try to make a deep counterbore I get a really bad finish. I'm running
the tool at 10k rpm (spindle range is 8k-25k rpm) and the finishing
pass at F300. I'm not sure what my F values actually mean, like in
ipm, but it looks like a good speed. I suppose my my options are to
use a carbide cutter, go to 6mm diameter (max on this spindle), or
adjust the feedrate and spindle speed. Can anyone take a look and make
suggestions? I know I should get myself a proper knee mill, but that's
not a realistic option for me at the moment. I'm hoping the machine I
have
http://i1262.photobucket.com/albums/...r1963/CNC1.jpg
will be adequate if I tweak the operation enough.

===========================

I suspect you won't like what you see if you put an indicator on the
head to measure deflection and pull on it with a spring scale.

I got a chainsaw finish from milling meter cutouts in 0.030" sheet
Aluminum with a 1/4" end mill with flutes 2" long, which I was using
to clear a forest of clamps. The reason was tool flex, not the
machine; a 1/2" diameter cutter gave a smooth finish at the cost of
more filing to square the corners.

My 700 Lb Clausing's spindle deflects ~0.001" per 25 Lbs.

-jsw


Ill have to agree. And I dont see if he is using a 2 flute or 4 flute
cutter..and in his case..its going to need to be a 2 flute. Slow the
feed rate way the frack down..something like 10-30 IMP would be
pushing it, partciularly with a single deep cut. Brass is brittle,
not real ductile like aluminum..but its still ductile and will load up
your endmill and plug that sucker up trying to unload chips. And of
course he is cutting it dry..which at those speeds..he should be at
the very least..using a mist coolant..not so much for cooling..but for
lubrication of the chips.

Gunner

"At the core of liberalism is the spoiled child,
miserable, as all spoiled children are, unsatisfied,
demanding, ill-disciplined, despotic and useless.
Liberalism is a philosophy of sniveling brats."
PJ O'Rourke