MetalworkingFun Forum

Pixman,

I have to part off sections of 304 stainless Steel, schedule 80, pipe, I have a parting tool that I'm currently using GTL 3.8 series inserts in. I have some no name inserts that are TIN coated and a few that are NPV (?) coated (all of them came with the tool from VME). Any idea on what kind of insert would be best, for me to use. The tool can use GTL, GTN and GTR inserts. Any idea on lathe RPM?


Thanks in advance

Jack,

I'd use a GTN (neutral, square tip) insert and cut at perhaps 250 to 300 surface feet per minute. I can't calculate actual RPM without knowing the diameter of the tubing. You can use a GTL or GTR if the tubing is a DOM (drawn over mandrel) seamless, I recommend the stronger neutral edge if it's welded because that weld tends to wipe out inserts.

The most important thing with stainless is to maintain a feed rate of at least .003" per rev and do NOT let it dwell for even a nansecond because it'll "work harden" on you.

As for grades and chipbreakers, stainless like a fairly sharp edge and tight chipbreaker. I'm not familiar with "NPV", is that the maker, chipbreaker or grade given?

The NPV is the coating, thats what written on the box (in pen). The inserts are dark gray, also the size is the only actual printed  info on the box tag, no name brand. Cutter was about $75 with 10 inserts, 7 tin coated and 3 NPV coated.

The size is 13/16" the approx size of 1/2" pipe

Jack,

The "NPV" may be TiAlN (titanium aluminum nitride) coated, or uncoated. Either way it's likely the better choice for that material.

It's going to sound crazy, but start at 1000rpm and .004" per rev feed. It should work fine.

Best of luck!

Ken

Thanks, Ken