Mystery cut-off tool holder

[Highpower]

Well I went ahead and took the cut-off tool holder off of his hands. It looked pretty much like the one Ken posted above with the 3/4" shank.



I had to mill the shank down to 5/8" to fit in my BXA tool post. Then I discovered my Phase II tool holder was bottoming out on the compound before the parting blade insert got to the lathe center line. So I ended up taking a little off from the bottom of the tool holder slot as well.

For a test run I tried parting off a deep well socket (after I had removed the chrome plating). Still, the chrome vanadium socket was extremely hard underneath. (I burned up a HSS end mill trying to cut some flats on the OD.)

I only got a couple of "C-5" inserts with the blade and I tried the un-coated one first. It cut through the socket pretty well on the first try. I went back to part off another section and all it did was rub.
I tried touching up the front of the insert with a fine diamond hone, which let it start to cut again - but barely.

So I switched to the only other insert I got which was TIN coated, and again it cut right through. I didn't make an attempt at a third cut. I think I need to try and find some GOOD inserts to fit this blade before I try going any farther with it.

Sigh......

[PixMan]

The biggest reason for parting inserts to fail is too low of a feed rate. They like to be pushed. If the insert is 3mm or 1/8" wide, you should be feeding at least .003" per rev, though .005-.008 is even better.

[Highpower]

Thanks Ken. These inserts appear to be about 2.2mm wide. On the first attempt I was feeding by hand but keeping steady pressure on the cut, and the chips were flying off of the insert (and breaking) beautifully. So I was expecting the very same thing on the next cut, but...... nothing.

As nicely as it was cutting on the first pass I'm sure I had to be doing something wrong to ruin the insert. 9/16" deep well socket (7/8" OD), 525 rpm, brushed on cutting fluid. The funny thing is I had removed the chrome plating first with a brazed RH tool bit on the lathe and it cut like butter.

That's when I took it over to the mill to cut some flats on the OD, and a good sharp 9/16" HSS end mill self destructed after traveling about 1/4" on a .010" depth cut.

Some days you're the dog... some days you're the fire hydrant.

When I get some more inserts I'll have to put on my big boy pants and try engaging the power feed next time. And pray.

Edit to add:
It just occurred to me....
I'm guessing it might have been caused by the interrupted cut?
(OD of the socket was milled into a hex.)