Surface Finish No. 5

[FH]

Hi Guys,
I am looking for the definition of "Sutface Finish No. 5".
What standard is it based on?
and
How can I measure or verify it on a piece?
Thanks in advance,

 

[tommac]

I am assuming that this refers to SSPC-SP 5, which is a 'white metal blasting cleaning' surface preparation. SSPC stood for the "Steel Structures Painting Council", but was recently renamed the "Society for Protective Coatings". Their web site is

http://www.sspc.org

 

[eromlignod]

Stainless steel is rated on a number scale, which is usually a very subjective one, but as far as I know there is no "5" in the scale (I don't know why). If the spec is really picky, you can use a profilometer to measure the finish.

Is it stainless steel?

Don
Kansas City

 

[tripleZ]

In tool & die terms, a #5 finish usually meant a 5 micron finish (shop jargon). Visually on a punch face, it usually meant you lapped it to a near mirror shine, finishing up with #3-#6 diamond paste (yellow & orange respectively) depending upon your polishing technique.

 

[eromlignod]

I doubt if it's a micron or micro-inch finish. This kind of finish would be called out in the familiar "check mark" symbol, not as "no. 5 finish".

5 is not a preferred number in either system. Micro-inch callouts would be numbers like

4, 8, 16, 32, 63, 125, 250, etc.

and the preferred metric ones would be

0.10, 0.20, 0.40, 0.80, 1.60, 3.2, 6.3, etc.

A finish of 5 microns would be pretty coarse, on the order of 200 u-in and equivalent to a sawn or drilled finish.

Don
Kansas City

 

[tripleZ]

Gotta learn not to throw the "n" in there...you're right on the micro-inch. A #5 was the equivalent of a 5 u-in. Thanks for the catch.

#5 would not be common, but for some reason a certain shop in NC (old customer) preferred to use odd numbers, specifically 1, 3, & 5.

 

[ornerynorsk]

This could also be an SPE callout, if it is referring to a mold finish.

 

[metalonis]

To further complicate matters:

http://www.letco.com/engineeringtables.php?value=3

 

[ewh]

"Surface finish designation like #4, #8 etc refer to the grit of the polishing media used to create the finish (for example #4 uses a grit of between 120 and 150 to obtain the surface polish)."

Thanks to GRoStruc in thread330-190474 and his link to the Specialty Steel Industry of North America.

http://www.ssina.com/publications/specs.html

 

[eromlignod]

...but only if it's stainless.

Don
Kansas City

 

[KENAT]

ISO 1302:1992 uses N numbers, could this be it?

http://www.roymech.co.uk/Useful_Tables/Surface_Texture/Sur_Fin_Values.html