TorqueMath

Speeds and Feeds Calculator

Spindle speed, feed rate, metal removal rate and cutting power for turning, milling and drilling. Pick the job and the material and you get a safe starting point. Change any value and everything updates.

Operation
Workpiece material
mm
m/min
mm/rev
z
mm
mm
mm
rpm
kW
Cut in progress

Starting values for every material

How it is calculated

Spindle speed comes from the cutting speed and the diameter that cuts. Cutting power uses the specific cutting force kc by Kienzle: it rises as the chip gets thinner, so light cuts need more energy per cm³.

Spindle speed n = 1000 · Vc / (π · D) rpm Turning vf = f · n Q = Vc · ap · f cm³/min Milling vf = fz · z · n Q = ap · ae · vf / 1000 Drilling vf = f · n Q = π · D² / 4 · vf / 1000 Chip thickness turning h = f, milling hm = fz·√(ae/D), drilling h = f/2 · sin 59° Specific force kc = kc1.1 · h^(−mc) N/mm² Cutting power Pc = Q · kc / 60 000 kW Spindle torque M = 9549 · Pc / n N·m Machine power P = Pc / 0.8 (spindle and drive losses)

Speeds are mid-range values for uncoated HSS and coated carbide with coolant. Material groups follow ISO 513 (P steel, M stainless, K cast iron, N non-ferrous, S heat-resistant, H hardened). kc1.1 and mc are typical handbook values. Start here, then raise speed until tool wear or chatter tells you to stop. Always follow the tool maker's catalogue for the exact grade.

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