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  for Metal Finishing since 1989
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Need help converting surface finishes

I am putting together an installation manual for some self lubricating bushings which my company has provided for a customer. The nature of the bushings require specific surface finishes for the shaft that they ride upon. I need to provide that info in the manual. I have received the perscribed finishes from the maufacturer (listed below), however they are unfamiliar to me. Can you help me to translate these into RMS? The are as follows...

General Precision (low load): d 8
General Precision (high load: e 7
High Precision: f 7

The only one I can seem to identify is the last one (f 7). Seems to be a 500 RMS.

I would be very grateful for any help you could give.

Joshua J. Smith
- Trenton, New Jersey
2005

I think there is a big confusion regarding american way and European way of specifing. US engineering standards for matting parts usually give a clearance for moving parts or interference for tight joints and then a surface roughness as an independent concept. DIN standards use letters and numbers as whole design concepts in a rather complicated way where everything is interrelated (clearance, size and surface finish). You need a copy of the standard to properly understand your customer.

Guillermo Marrufo
Monterrey, NL, Mexico
2005