See attached. The user selects the alloy and enters the stock diameter. The formula for the RPM then is (I think):
=IFERROR(12*VLOOKUP(A2,MaterialSFPM,2,FALSE)/(PI()*C2),"")
Since the vlookup to find the SFPM is included in the formula, the SFPM column is superfluous and can be deleted.
For 1/4" stock brass, the formula returns 2292. If this is overly precise and you would like it rounded to the closest hundred (included as RPM rounded):
=IFERROR(ROUNDUP(12*VLOOKUP(A2,MaterialSFPM,2,FALS E)/(PI()*C2),-2),"")
For the closest, ten, change that -2 near the end to -1. Easy peasy. :-) It would probably be a good idea, once you have it all fleshed out, to lock any formula cells and protect the sheet. If you need any further help with that or anything else, let me know.
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