"Karl Townsend" remove .NOT to reply
wrote in k.net:


"Kristian Ukkonen" wrote in message
...

Hello,

I have a problem with a MCLN boring bar insert.

It works ok with a "normal" CNMG insert, but I just can't
get it to work with the Mitsubishi -FS finishing chipbreaker.
Material is just mild steel, finishing diameter about
60mm. I get totally crazy chatter - huge surface "waves"
to the turned surface (which looks really smooth except
for the large waves) - it REALLY sings. =

I've tried depth of cut 0.1 - 0.25mm, feed 0.08 - 0.22 mm/r,
and many surface speeds - less speed makes less chatter,
but not that much effect (180 - 700 RPM tried). These same
speeds/feeds/DoCs work with a normal CNMG insert, the problem
is only with the -FS insert.

What's going on? I've never experienced chatter like
this before. The boring bar is 32mm diameter!!!!!
Should have no problem with a really small chipload like this.
The tool is at center height, and I've tried lowering
and increasing height a bit, but that hasn't mattered.
The lathe weights about 2000kg and is very rigid.

Any ideas? I've not used the -FS geometry before, so there
could be some trick but it sure ain't clear to me what
it could be..

Kristian Ukkonen


I'm guessing something is rubbing - no cutting relief angle. I took
the liberty of cross posting this over to alt.machines.cnc because
there's some really sharp guys over there. Maybe they will have a
better answer.

Just for grins, have you tried this insert on an O.D. cut; facing or
turning?


First off a boring bar should be slightly above center to prevent
chatter. Second the FS geometry is intended for Stainless Steel. For mild
steel you should be using an FH geometry.

Good Luck.


--

Dan