Have been spending quite some time looking at various metric drill speed charts and can't find an exact answer for surface speed. I can find RPM, once surface speed can be determined.

(4 x surface speed) / 0.625 diameter.

 

An exact answer is not necessary, your spindle probably doesn't go that fast.

Alumuinum ~ 400 Feet / minute = 25K RPM

 

Do you have a source for the 400 feet/ min so I can show my work to the teacher?

 

As this is homework, what have you done to solve the question?

If you want the surface speed, search on "speeds and feeds" for whatever substance on which you are working. Aluminum is generic. You will find different results for different alloys. But, your instructor probably just wants a typical setting for a common alloy,