Summary for 30 ra to microns Discussion
30 ra to microns is the core question here: Jeff asked how to convert an American supplier’s Ra finish values into microns so he could verify whether impression rollers met a stated 32-63 micron tolerance. The reply explains that there are about 39.37 inches in a meter, so there are just under 40 microinches in a micron. Using that relationship, an Ra of 30-40 microinches works out to roughly 0.75 to 1.0 micron. The answerer also cautions that the metric tolerance may be misstated, because 32-63 microns would be far rougher than 30-40 microinches; he suspects the intended requirement was actually 32-63 microinches. The practical takeaway is to confirm the units before judging whether the rollers are within spec.
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
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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