CRS 1018 Tooling Help

[fhadk]

Hi everyone.
I am having trouble getting a good finish when turning 1018. Part is 1.25" dia by 9.25" long. Turning down to .75 " 8.5" long. I am having slow way down to get a chatter free cut resulting in a crap finish.
I found a few threads related to my problem, and people said to use a positive insert. So my question is, do they mean an insert with a more positive chip break or a positive rake tool holder.

I am currently using a MCLNR with a CNMG431MP. This works great for 1018 when part is robust and can keep the speed up.Thanks for any advice/help you guys can muster.
Jesse

[MFassler]

thats cause cold roll sucks for finish! positive chip breaker!

[g-codeguy]

Use both. The two combined should let you increase RPM a bit. Go with a ground insert. Preferably a cermet. Hard to get a good finish with too slow of an RPM. Use oil if possible.

[DareBee]

It is likely because your part is expanding (thermal) and your tailstock is forcing it to orbit.
I find that it helps to leave the tailstock spindle unlocked and leave the pressure at absolute minimum.
What you are doing is PITA.

[g-codeguy]

I assumed a cnc lathe. Which type are you using?

[fhadk]

It is a Haas SL-30. Thanks for the replys. I have some 12L14 coming today to get me through this part. I will definately be ordering some positive tooling though for the future.
Thanks again.
Jesse

[MetalProBow]

if you lookin for good finish when turning you could try using wiper inserts with a light chipload