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In need of any information regarding a #4B finish on 316 SS Pipe

(-----) 2007

Hello. I work for a supply company and had a customer ask me for some 316L stainless steel pipe with a 4B finish on the OD. My customer is a fabricator for an end user and was not able to supply me with any more information than that. Does anyone have any information regarding what this finish is, what RA it meets, or any sources for more information for that matter? Thanks.

Doug Wills
Sales - Salisbury, Maryland

January 6, 2008

I don't have a specific RMS or Ra number for you, but any metal mill should have that for you with certifications. I'd go with the certs than a verbal generality, because there maybe some variations due to the metal hardness and the processing rolls.If you want a generalization, mill steel comes in at around 35 RMS and a 4B maybe around 25 or a little better.

tony kenton
AF Kenton
retired business owner - Hatboro, Pennsylvania

January 12, 2008

If I remember correctly, the 4B finish is a brushed finish can range from 8-20 it was posted on several years ago and


there is the link to the post I was speaking of.

I don't think the actual finish matters as long as the 4B is between 8 and 20.

Ryan Cook
Ryan Cook
Toccoa, Georgia

January 23, 2008

In my 40+ years in the non-ferrous metals industry I have never heard of a #4B finish. A #4D finish is common to the industry (A.K.A. Dairy Finish) this finish is measured in the number of pits allowed per square foot of material.

To achieve the reflectivity of a #4D finish you would have to get to something like a 15-20Ra - though this may not pass the pit test.
Not sure if anyone does pipe in this polished finish.

Phil Parsche
- Pleasant Prairie, Wisconsin

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