Questions about chipbreaking inserts.

We are running chip breaking inserts on our CNC retrofit lathe. (13x40,
2 HP)

We've got a little problem with swarf buildup, actually a big problem.
When we machine a part of considerable size, removing a significant
amount of material, the swarf will build up around the chuck, choke the
coolant flow to the tool, etc. We often can't run a complete program in
one go without having to periodically stop and clean things out. This
becomes a big pain.

Details: we are running TCMT321 (7 degree rake) inserts. This weekend
we were machining 3" diameter 4140 steel parts. Total volume of
material removed was about 6 inches^3. We were turning at 750 RPM,
feeding a nominal F6 on a 20 thou cut. By nominal, I mean that someone
might have been running a 50 to 300% feedrate override. Our tool height
is set almost exactly at center height.

The "chips" we were getting off are really 6" to 18" long swarf
stringers. We have machined steel and gotten actual chips off, but I
can't remember exactly when or under what conditions.

Questions:

a) what sort of chip breaking performance should we be seeing ?

b) would the lack of chip breaking performance have anything to do with
running a relatively small insert (ie 321) for the depth of cut ?

c) how does one prevent a massive buildup of swarf in and around the
chuck and tooling ?

Thanks in advance,

Kim



--
Kim Lux <lux@...>