Formulas. Speeds Inch. SFM = surface feet per minute. RPM = SFM X / Tool Diameter. Speeds Metric . SMM = surface meters per minute. RPM = SMM X / Tool Diameter. Radial Depth of Cut in Percentage of Diameter. 50%. 30%. 20%. 15%. 10%. 5%. 1%. CLF = chip load factor. Feeds Inch. IPM = inches per minute IPT = inches / tooth. IPM = RPM X number ...