Feed Speed
Is feed speed the same as spindle speed?
No. Spindle speed is revolutions per minute (RPM), while feed speed is the linear advance rate of the tool through the workpiece.
What equation is used most often?
Feed Rate = RPM × Number of Flutes × Chip Load per Tooth.
Why does chip load matter?
Chip load determines the thickness of material each tooth removes per revolution, directly affecting tool life, heat generation, and surface finish.
Feed speed in CNC machining is the linear rate at which the cutting tool advances through the workpiece. Commonly expressed in inches per minute (IPM) or millimeters per minute (mm/min), it is determined by spindle speed, number of flutes, and chip load per tooth. Proper feed speed ensures efficient chip removal without rubbing or overloading the cutter.
On the shop floor, feed speed is set based on material, tool geometry, and operation type. For a CNC router or mill, the core relationship is Feed Rate = RPM × Number of Flutes × Chip Load. Programmers specify different feed rates for lateral cutting, plunging, and contouring. In woodworking and edgebanding, feed speed directly affects edge quality, tear-out, and glue-line performance. Production crews tune feed to balance surface finish with cycle time. Too low a feed causes rubbing, heat buildup, and premature tool wear, while too high a feed overloads the cutter, induces chatter, and risks breakage. Correct feed ensures each cutting edge removes a controlled chip thickness, maintaining tool life and part quality. Adjustments are often made based on chip evacuation and machine dynamics.
Rubbing and Heat: Feeding too slowly causes the tool to rub instead of cut, generating excessive heat that dulls edges and can scorch wood or melt plastics.
Chip Recutting: Feeding too fast for chip evacuation leads to recutting of debris, increasing load, degrading finish, and risking tool chatter or breakage.
Z-Feed Mismatch: Using XY contour feed rates for plunge or ramp moves overloads the tool tip, causing breakage, breakout, or machine stalling.