Please Help Turning 440c

[HSPMInc]

I'm turning some parts out of 440c and there's a finish callout. I'm getting good finish but going through tools like crazy. What's the recommended starting SFM for 440c. Also does anyone have any good recommendations on an insert/grade/coating that has worked well for you? This job is killing me so any help would be appreciated.

____/\/\/\/\/\/\/\/\/\/\____
|___........................____|
......\/\/\/\/\/\/\/\/\/\/
Thats what the part looks like and I'm using stellram 35deg .008r VBMT inserts. Ignore the periods. Had to do that to get it to look right.
I'm chained to 35 deg and .008r tool because of the design of the part. Grade MP-37 is what I'm using now. I'm open to buy anything if it will work better. I'm only getting about 20-25 parts per corner right now. With a .005-.01 DOC. I'm just using this tool as a finisher so I can take as little or as much as I need to.

Thanks again for any help.

[CNCRim]

What's the finish callout to be? 25-30part/corner is normal. Try bigger radius nose it will last better and the finish easy to keep.

[HSPMInc]

The finish callout is basically perfect, and I can't use a bigger radius tool. .008 is the biggest I can go on these parts. The radius in the bottom of each groove is too small for anything bigger.

[PixMan]

What is the I.C. size of the VBMT inserts you are using? What is the stock diameter vs. finished size (depth of cut)?

Valenite has a recently-introduced grade that's working excellent in 440C, but you have to try and keep the SFM up over 500 for it to work well. Here's two different size inserts in that grade, call any distributor for price & availability:

VBGT 220.5 PF3 grade 9605
VBGT 330.5 PF3 grade 9605

These are a sharper (ground periphery) insert than you've been using, so it should cut freely compared to a VBMT. Chipbreaker designed for feed of .004 to .010 ipr at depth of cut from .005" to .080".

Good luck!