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  for Metal Finishing since 1989
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RMS-RMZ callouts on auto parts cause confusion

We have a Japanese customer who has a machined surface callout of 1.64 s and a 3.** something on z! My questions is: does the z = the average of the highs and lows of the finish and the z really rmz? the s = the mean to the high of the finish and the s really rms ( root mean square)? The customer really isn't helpful on this at all!

Sandy Metzger
supplier to Automotive Industries - Minor Hill, Tennessee, USA
2003

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Hmmm. It sounds as if you have a communication problem and to guess or ass-u-me (second meaning) anything would be nothing but trouble. I suggest you ask the customer for a sample of a finished acceptable part or tell him you will match his finish. If that is not acceptable to him, restate your finishing requirements on him knowing what is good acceptable standards for your industry or the parts end use.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2003

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According to ISO 4287, Rz is defined as the sum of the height of the largest profile peak height Zp and the largest profile valley depth Zv within a sampling length. I have no idea what s is supposed to mean. Rq is the root mean square deviation of the assessed profile. I suggest you and your customer use the precise definitions given by this consensus standard in order to remove any confusion.

Toby Padfield
Automotive module supplier - Michigan
2003