Surface Finish Callout

[AmeristarQA]

I recieved a print from a customer and they are requesting a surface finish, and all the specify is 8.20/C I am not familiar with this, is there anyone out there that recognizes this?

 

[DennisP]

If it is a turned surface, then the C probably denotes a circular lay to the finish. If the part is metric, then the 8.2 most likely means an 8.2 micron Ra finish. If it's an inch print, then it woulod be 8.2 microinches which would need to be a ground surface. A better answer might come from the customer.

 

[eromlignod]

I doubt if it is either microns or microinches. 8.3 is not a preferred number in either system. Micron figures use a number series like

0.2, 0.4, 0.8, 1.6, 3.2, 6.3 etc.

Microinch finishes would be

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

An 8.3 um finish would be extremely rough...like the finish from sawing or from a shaper. 8.3 u-in would be a fine-ground finish, but would always be denoted as simply "8" in the familiar "check mark" finish symbol. The .3 mantissa would be ridiculous.

Don
Kansas City

 

[WaterMan22]

I would check with the customer for clarification. They may be trying to designate: 0.2um and 8u-in, which are synonymous on the Ra scale.