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topic 59806

Surface quality requirement for raw material which will be polished and plated

February 25, 2015

Q. Hello,

I am currently working in an electroplating workshop. We are doing high-quality decorative metal finishings : parts are hand-polished (usually 180 and 320 belt sanding, sisal cut, color buff) and plated manually in Nickel, Gold, Chrome, black nickel... Most of the parts are made from machined or profiled aluminium.

Both customers are asking to me for the quality surface requirements of the raw material. Usually, I answered : " without pits, scratches and deep machined lines". I would to supply a guideline to the engineers from the customer companies who are designing the parts. My question is : how could I translate "without pits, scratches and deep machined lines" in engineering words? Is Ra roughness accurate ? I heard about Ra 3.2 (metric unit) on visible (to be polished) areas...

Thank you,


ps : Sorry for my written english, I try to be understood and clear but I am French... :-)

Nicolas Duthil
Project coordinator - Bordeaux, Gironde, FRANCE

March 5, 2015

A. Standard practice is to designate either an Ra or Rms. That should be noted on dwg's for general guidelines. Additional notes such as you mentioned can be added. Sometimes you can also note what post treatment is such as plate, paint, etc. and that also helps determine the vendor.

tony kenton
AF Kenton
Hatboro, Pennsylvania

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