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plating, anodizing, & finishing Q&As since 1989

"Speeds and feeds vs. surface finish"

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2005

WHAT IS Ra VALUE? HOW CAN Ra VALUE BE MEASURED? WHAT IS THE DIFFERENCE BETWEEN Ra AND Rz? IS THERE ANY FORMULAE, WHICH CALCULATES AND GIVES THE FIGURE OF SPEED AND FEED IN CONNECTION TO THE DIAMETER AND CUTTING SPEED, SO THAT WE CAN PRODUCE THE PARTS ON A CNC WITHOUT A NECESSITY OF CHECKING THE Ra VALUE, AFTER THEY ARE MACHINED?

Jacob Ebanezer
forging & turning - Jamnagar , India

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2005

Hello, Ebanezer, welcome to finishing.com. Please try our search engine at the left of this page because your first three questions have been answered many times already. Certainly the slower the feed and faster the speed, the finer the finish. But I think you need to name the substrate material and the cutting tool material before the fineness of finish can be projected. Maybe a specialist will correct me.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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2005

Ted gave you some information that maybe of help; however, let me give you the short cut. Get a profilometer. A good one will have a programmable or scale selection which can measure on at least 2 or 3 scales. There are no good manual systems because of the human factor.

AF Kenton
retired business owner - Hatboro, Pennsylvania