Small diameter S7 turning job

I'm doing a 500pc job that uses 3/4" S7 tool steel, 3" sticking out of the jaws. Final turned diameter is 0.190 and the part length is 2.3". I need .7" to clear the ER16 collet nuts holding the live tools. The 3/4" bar is required for a milled feature that protrudes .330 from the center.

In order to keep chatter down, my SFMs are only 75-200. The further I am from the chuck, the lower the SFM. Also, the part needs sixteen .080" holes drilled in it. I'm feeding at 0.5ipm @ 2000rpm.

The parts are coming out fine, but the low SFM and high material removal requirements are giving me 20 minute cycle times. Also, for some reason, my stainless inserts are working better than my steel inserts.

Any tips on working with S7?

What size tool nose radius are you using? I would think that using an insert with an .008" or .004" radius would tend be better than say .016" or greater. S7 is usually pretty nice to turn, but I've never gone that far down on diameter using my turning center, only on the manuals.

It would be my guess that you find your stainless inserts working better because typically, inserts for stainless have a thinner CVD or sometimes even a PVD coating to give more edge definition to an already free cutting edge- in order to reduce work hardening. But in your situation, this free cutting edge is working well on your smaller diameter part due to less tool pressure- more free cutting, and getting more heat out in the chip instead of into the part & insert.

I agree, use a 1/64" or less nose radius, medium-finishing edge chipbreaker, and possibly even a single sided insert.