Feed Rate

Feed rate is the speed (in inches per minute) at which the cutting tool advances into the workpiece, and combined with spindle speed, it determines the chip load and therefore the tool's cutting efficiency and surface finish. Too slow a feed rate causes rubbing, heat buildup, and poor surface finish, while excessive feed rates overload the tool, causing deflection, chatter, and premature failure.

The relationship between feed rate and spindle speed is mathematically linked through the formula: Chip Load = Feed Rate ÷ (Spindle Speed × Number of Flutes), making correct calculation essential for all CNC programming. Cutting tool suppliers publish recommended feed rates and speeds for different materials and tools, providing starting points that experienced programmers and operators refine through test cuts and optimization.

Modern CNC machines with live tool monitoring can automatically adjust feed rate based on cutting forces, maintaining optimal conditions throughout a program and preventing unexpected tool failure.