30 RA to Microns

How do you convert from English Ra to microns. I need to have impression rollers grinded down to somewhere between 32-63 microns but my American supplier uses Ra. The surface finishes that they provided us ranged from 30-40 Ra. Is there a simple way to convert this? Are they within our metric tolerances?

Thank you!

Jeff B
Plant Shop Employee - St. Louis, Missouri
January 5, 2011

Hi, Jeff.

There are 39.37 inches in a meter, so there are just under 40 microinches in a micron. An Ra of 30-40 microinches would thus be an Ra of about .75 to 1.0 micron. I suspect that your in-house terminology is wrong and that you actually require an Ra of 32 to 63 microinches.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Ted is available for instant help
or longer-term assistance.
January , 2011

Q. Can anyone tell me what 150 microns would be in an Ra finish?

Thank you,
Danny

Danny Ostrander
- Gelnwood, Minnesota, USA
January 11, 2012

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