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topic 9267

Ra - roughness clarification


Can someone explain exactly what is being measured in an Ra surface roughness spec. Is it an average of the peak to valley heights over the measured surface?

John Cianciolo
- Salem, New Hampshire, USA


The Ra is an average of the peaks an valleys of a surface finish. The difference in the highest peak and lowest valley is commonly referred to as the Rmax.

Daryl Spindler
- Nashville, Tennessee



To add to Daryl's answer, I'd refer you to where there is a nice explanation of all those pesky lookalike surface roughness parameters.

Good luck!

lee gearhart
Lee Gearhart

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