Speeds and Feeds Calculator
Calculate spindle RPM and feed rate for milling or turning
Frequently Asked Questions
RPM = (Cutting Speed × 3.82) ÷ Tool Diameter, using cutting speed in surface feet per minute (SFM) and diameter in inches. In metric units, RPM = (Cutting Speed in m/min × 1000) ÷ (π × Diameter in mm).
Feed rate (inches or mm per minute) = RPM × Chip Load (per tooth) × Number of Flutes. Chip load is the thickness of material each cutting edge removes per revolution — too low causes rubbing and heat buildup, too high can break the tool.
Cutting speed is how fast the material moves past the cutting edge, determined by the material being cut and the tool material (carbide vs. HSS). It's a property of the material/tool combination, not the machine — look up recommended SFM/m-min values from your tool manufacturer's chart for your specific material.
Too light a chip load causes the tool to rub instead of cut cleanly, generating excess heat and wearing the tool prematurely. Too heavy a chip load can overload and break the tool or stall the spindle. Manufacturer-published chip load ranges per tool diameter and material are the standard starting point.
Use the material preset for a reasonable carbide-tool starting SFM, then adjust based on your specific tool coating, machine rigidity, and coolant — these are commonly published starting points, not exact values for every tool/material combination.