Posted by: Tommy Dong ® 07/07/2006, 01:43:31 Author Profile eMail author Edit

There is Raceway finish requirement for ball bearing ring what says" Must be finished to 10 micro inches AA or Better. 1. Could somebody help me to transfer this unit of "inches " to "mm"? 2. What is the AA mean?

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Re: 10 micro inches AA or better
Re: 10 micro inches AA or better -- Tommy Dong	Post Reply	Top of thread	Forum

Posted by: Kelly Bramble ® 07/07/2006, 08:05:39 Author Profile eMail author Edit

AA = arithmetic average of the absolute values of the measured profile height deviations divided by the evaluation length, L. This is also known as Roughness average (Ra). Alot of designers and engineers mistakenly refer surface roughness as "RMS". I think they mean root mean square. Nothing special here, other than they are asking for a 10 Ra finish. 10 microinches Ra is equal to approximately 0.25 micrometers Ra, or in your case AA. This is not a cheap finish to manufacture.. Modified by Kelly Bramble at Fri, Jul 07, 2006, 08:12:55

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