Need Help!- Parting off Stainless Steel

[JWB_Machining]

Hey,

I'm trying to machine some British Stainless Steel that the engineer who gave it to me said was 9515. I turned and faced the piece of stock I was given to a diameter of 5.820". I have just over an inch hanging out from my chuck. I'm trying to part this off with a thickness of about .150" so I can grind the disc down to 0.100" I'm having trouble parting off though, All I can seem to do is get the whole thing to squeel at me and go between brown and silvery looking chips. This is with my cut off tool only hanging out 1.3" from my tool post, lord knows what'll happen when I have it hanging 3.1" over. Does anyone have any advice for parting off stainless so that it doesn't scream so loud, the way it sounds just lets me know it's not right. I'm trying to part it off by hand so I can find the right feed but I'm having no luck.

[djr76]

Slow it down, sounds like you are going way to fast. Try around 200 rpm.

[PinMan]

I part off 4" dia. 17-4 on a regular basis. This is what I work with.

If I am using my Okuma manual lathe with auto feed:

Kennametal GS125R12 insert (KC720 Grade - great for SS)
127 RPM
.002 IPR
Oil for lube (drench it )

It is very slow going on a big part, but you keep the heat down and your holder doesnt walk.

If Im using my CNC:

Same insert
Constant surface speed for the type of material.
For 17-4 Start at 200RPM with a 3000RPM cap
50 SFM for my CSS
Use coolant.

Hope this helps ya out some.