TG&P vs Finished CRS

[DJKinMaine]

I'm trying to determine which would be most cost effective: to have CRS finished to RMS-20 or use TG&P. Shafts will be used on a bearing surface at low RPMs. What are the RMS values for TG&P and CRS?

 

[BobUXL]

Besides the cost, you need to examine the level of defects you can tolerate. Cold finished steels, in particular stainless steels are governed by ASTM A-484, which outlines defect levels as well as bar tolerances. A cold finished bar can have defects up to 1% bar diameter. Turned, ground and polished bars have better tolerances than cold finished products and are relatively defect free. but you could subject yourself to potential trilobe conditions in the diameter.

Bob

 

[mewhg]

Bob,

What's a trilobe condition and why is TGP bars subjuct to it?

many thanks
Bill