feedrate

Feedrate is the speed at which the cutting tool moves relative to the workpiece, or the workpiece moves relative to the tool, during machining. In CNC terms, it is the programmed movement speed along the cutting path and is typically expressed in distance per time, such as millimeters per minute (mm/min) or inches per minute (in/min). It is controlled by the feed rate (F) instruction in G-code and is distinct from spindle speed and cutting speed.

In turning, feed rate F equals the feed per revolution f multiplied by the spindle speed n (F = f × n). In milling, F equals the chip load per tooth f_z multiplied by the number of teeth z and by the spindle speed n (F = f_z × z × n). These relationships connect tool geometry, material removal rate, and machine performance.

Factors influencing feed rate include material hardness and machinability, tool diameter and flute count, tool material and coating, rigidity of the setup, coolant, and the desired surface finish. Feed rate interacts with cutting speed, depth of cut, and stepovers: higher cutting speed can allow higher feed rates up to a tool’s capacity, while excessive feed can cause rubbing, tool deflection, and accelerated wear.

Practical use involves optimizing feed rate to balance material removal rate with surface quality and tool life. Many CNC machines offer feed rate overrides to adjust during operation, and programmers select starting values based on tooling catalogs and test cuts to achieve the desired balance.

See also: cutting speed, chip load, feeds and speeds, spindle speed.