Work out spindle speed instantly with clear inputs, formula shown and shareable results.
Spindle speed is the cutting speed relation rearranged: rpm = 12 x SFM / (pi x diameter). Handbook cutting speeds are properties of the material and tool pairing, so this is the step that turns a recommendation into a machine setting.
Spindle speed
rpm = 12 x SFM / (pi x D in)
rpm = 12 x SFM / (pi x D in). Spindle speed is the cutting speed relation rearranged: rpm = 12 x SFM / (pi x diameter).
Only on rigid setups with good coolant. Speed drives tool wear far more strongly than feed does, so starting mid-range and increasing while watching the edge is the safer route.
This calculator takes 2 inputs: Recommended cutting speed, Tool diameter. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.