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Surface finish versus cost chart

I am the group supervisor in the prototype R&D machining group. I am seeking to educate new engineers and scientist on the expense of the specific callouts they use on drawings. The main question is: Has a chart been developed that shows the relative cost associated to the surface finish callouts? (Example 64rms is "z" dollars 32rms is "z" x 2 dollars 8rms is "z" x 5 dollars)

Darrol Houser
Space craft - Pasadena, California, USA
2004

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I know of no such list and I don't think anyone can come up with one. The reason being that there are just too many factors. I tried to classify equipment systems by the amount of material removal they can achieve; however, that was not very specific. Meaning, it identified the aggressiveness of a system in relationship to part sizes based upon 5 classifications of material removal equipment/ processing systems. Even this list used a wide range variation because mechanical systems use different abrasive sizes and energy systems or application of energies and matter.

AF Kenton
retired business owner - Hatboro, Pennsylvania
2004

Back one time when I was studying engineering, I recall there was a Manufacturing Process text book with just the input you want. I cannot remember the details but the curve was exponential with cost increments anywhere from 50 to 100% fold with every additional step required to go from: 1-rough machine, 2-medium, 3-fine, 4-coarse ground, 5-fine 6-coarse lap and 7-fine lap. This chart was prepared with roughness as well as tolerance in mind, so it might not be applicable when aspect is the only desired feature. It indeed emphasized on the rate of rejects as a very important variable. The better the finish a part requires, the higher the probability of a reject and the higher the added labor cost at the moment of the reject, so the total cost adds up.

Guillermo Marrufo
Monterrey, NL, Mexico
2004