The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Help with how a surface finish is labeled

I have several drawings which tolerance the surface finish of a part. The figure used for surface finish is a combination of the square root symbol and the number 125 (125 in small font as superscript to the square root symbol). What is unusual is the same surface finish spec is listed for a raw steel part (CR CQ) and for a powder coated part. Neither my steel supplier nor my powder coat supplier can identify the symbol. What is being specified?

John Backscheider
fabrication and metal stamping shop - Fairfield, Ohio
2003

---

It's actually supposed to be about half check mark and half square root symbol. The '125' means a surface roughness value of 125 microinches as measured by profilometer. This notation is a way of specifying surface finish that neither implies nor precludes a metal removal operation, so it is valid for a raw steel part as well as a finished part.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2003

I have many surface finish requirements in the drawing released from research and development. But the ambiguity here is to arrive the exact finish requirement from those triangle symbol . I have tried to find out the Ra value by referring thru, design data book, but there are 3 values related to same symbol. I can't able to find out Ra value for single triangle.so kindly help me come out of this problem.

Prakash
- Chennai, India
2006

---

Sorry, I've not personally familiar with that system for indicating surface finish (in my drafting experience a triangle with a number in it only meant see the note of the same number), but please see letter 11700 as it sounds like it addresses your question. Good luck.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2006