Feed Per Tooth

Feed per tooth (F_z) is the linear chip thickness or chip load removed by each cutting edge of a milling cutter as it passes through the material, usually expressed in mm/tooth or in/tooth. It is a fundamental parameter used to calculate table feed rate via the formula Feed rate = RPM × number of teeth × feed per tooth, directly linking spindle speed, flute count, and material removal for efficient cutting.

In CNC milling, the programmer or setup technician starts with the toolmaker’s recommended chip load, then converts it to a feed rate using spindle RPM and flute count before posting the program. For example, if a cutter has 4 flutes, runs at 10,000 RPM, and the target feed per tooth is 0.05 mm/tooth, the table feed becomes 2,000 mm/min. In real production, F_z is adjusted for material, cutter geometry, and chip thinning—at low radial engagement, the actual chip thickness is less than programmed, requiring feed corrections. This parameter directly affects chip evacuation, surface finish, tool wear, and whether the cut is shearing or rubbing. Too-low F_z makes the tool rub, generating heat and poor finish; too-high F_z overloads teeth, raising cutting forces and risking chatter or tool breakage. Tool data sheets and feeds-and-speeds calculators use the same logic: determine an acceptable chip load for the tool/material pair, then compute the feed rate.