On Dec 26, 4:48*pm, "Wild_Bill" wrote:
Grooving and parting off require a rigid setup, which you may already know,
Tim.
Snug everything down except the cross feed, and even the cross feed if there
is much backlash in the feed threads.

Including the carriage lock.

A very sharp cutting tool with the proper relief angles and possibly a chip
breaker are mandatory. I find that a very slight front relief angle prevents
the tool from grabbing or self-feeding into the workpiece. When the front
relief is almost vertical, the tool tends to rub instead of self-feeding.

My Multifix parting holder and Enco bit work pretty well most of the
time. I don't claim to understand exactly why but I'll describe it for
you. If anyone knows better, listen to them instead. I'm almost
totally self-taught and some of this may be simply adapting to the
quirks of my lathe. "I do this..." is my code for YMMV.

The holder slopes the bit 4 degrees for top rake. The front rake is
presently 16 degrees on the bit, or 12 WRT the work. That may be
excessive. I think the minimum is 5.

I hollow-grind the end so a hand-held stone touches only the cutting
edge and the lower heel. With heel contact to guide it, the stone
doesn't rock vertically when I clean up the edge every few minutes in
SS, or weekly in Al. It rounds the end laterally but that doesn't seem
to matter.

The bit protrudes about 9/16" to cut off up to 1" rod in 5C collets.
It definitely works better at half that.

I grind square across, so the bit leaves a tit on the cut-off part.
Grinding the end at a small angle is said to cure this, but with 9/16"
of protrusion the 0.062" x 1/2" bit flexes too much from the side
thrust.

I use a needle oil bottle to slowly feed oil into the slot. The tip
usually rides along the bottom. This is tedious and boring but if I
stop or try brushing the bit often jams within a minute. The belt is
loose enough that I only have to push the cone pulley backwards to
free the bit, back out, then feed very slowly until the ticking stops.

For a repetitive job I soon get the feed figured out and use the auto
crossfeed.

Make sure that the cutting tool is being fed as perfectly perpendicular to
the workpiece as you can get it.

I tighten the toolpost bolt with the cutoff holder pressed against the
end of the spindle or the collet adapter.

A quality cutting lubricant applied right in the groove can make the
difference between success and, well, problems.

Home Depot pipe threading oil works for me on SS, drill rod and
aluminum.

A slow spindle speed has worked best for me and depending upon the diameter,
it may need to be very slow.
Crawling slow is not fast enough for aluminum, but slow doesn't seem to be a
problem with mild steel.
WB

See/hear chatter, slow down a step. I've only used the backgear when
parting 3" steel, a job I had to complete with the bandsaw.

"Tim Wescott" wrote in message
Now, I'm trying to turn some fins into a replacement cylinder for a Cox
15. *I basically made myself a narrow little cutoff tool, which started by
chattering a little bit, then rapidly evolved to chattering a lot, then
bound up, wrenching the cylinder blank out of the chuck and breaking the
tool.
Tim Wescott

I make delicate things on the end of solid rod stock held in a collet
and often with tailstock support as well.
How deep are the slots?

Jim Wilkins