Surface feet per minute (SFPM or SFM) is the combination of a physical quantity (surface speed) and an imperial and American customary unit (feet per minute or FPM).
It is defined as the number of linear feet that a location on a rotating component travels in one minute.
SFM is a combination of diameter and the velocity (RPM) of the material measured in feet-per-minute as the spindle of a milling machine or lathe.
The faster the spindle turns, and/or the larger the diameter, the higher the SFM.
The goal is to tool a job to run the SFM as high as possible to increase hourly part production.