Cutting force and power calculator

The three cutting force components

• Cutting force Fc: acts along the cutting speed. Power and torque come from this force.
• Feed force Ff: along the feed. In drilling it is called thrust, and it loads the feed axis and the workholding.
• Passive force Fp: pushes the tool away. It bends slender work and causes chatter.

How it is calculated

Chip thickness h = f × sin κr (milling: mean chip thickness hm ≈ hex ÷ 2)
Specific cutting force kc = kc1 × h^−mc × (1 − γ0/100)
Turning Fc = kc × ap × f  Pc = vc × ap × f × kc ÷ (60 × 10³)
Milling Pc = ap × ae × vf × kc ÷ (60 × 10⁶)
Drilling Pc = f × vc × D × kc ÷ (240 × 10³)  thrust Ff ≒ 0.5 × kc × (D/2) × f × sin κr
Torque M = Pc × 30 × 10³ ÷ (π × n)  motor power needed = Pc ÷ η

• Maximum chip thickness in milling is hex = fz × sin κr × 2√(D·ae − ae²) ÷ D when ae is smaller than D/2 (otherwise hex = fz × sin κr). The mean thickness is taken as half of hex; this underestimates it, so kc and power come out on the safe (high) side.
• Drills are taken as two-flute: chip thickness per lip is (f ÷ 2) × sin(point angle ÷ 2).
• η is the drive efficiency. Tool makers use 0.7–0.9 (0.7–0.8 for belt or gear drives, close to 0.9 for built-in spindle motors).
• Spindle motors have a continuous rating and short-time (30 or 15 min) ratings. For continuous cutting compare with the continuous rating and leave a margin. At low speed the motor runs short of torque before power, so check torque as well.

Related calculators

For speeds and feeds, see the turning, milling and drilling calculators. Material data is in the materials section.