Drilling calculator

Enter the drill diameter, cutting speed and feed per revolution; spindle speed, penetration rate, removal rate and drilling time follow. Add the Kienzle constants and the force on each lip, the net power and the torque are computed too.

Live

Drill diameter Dc mm

Which one is known? vc n

Cutting speed vc m/minSpindle speed n rpm

Feed per revolution fn mm/revPoint angle σ °

Hole depth L (full diameter) mm

Specific cutting force kc1.1 N/mm²Kienzle exponent mc

Take kc1.1 and mc from the material page or the tool maker’s catalogue. Point angle: commonly 118° on HSS drills and 140° on solid carbide drills.

Kinematics

—rpmSpindle speed n

—m/minCutting speed vc

—mm/minPenetration rate vf

—cm³/minRemoval rate Q

—mmPoint length lp

—minDrilling time tc

Force, power and torque (Kienzle)

—mmChip thickness per lip h

—N/mm²Specific cutting force kc

—NCutting force per lip Fc

—kWNet power Pc

—N·mTorque Mc

Formulae

n = \frac{v_{c} \cdot 1000}{π \cdot D_{c}}

v_{f} = f_{n} \cdot n

Q = \frac{D_{c} \cdot f_{n} \cdot v_{c}}{4}

l_{p} = \frac{D_{c}}{2 \cdot \tan (σ / 2)}

t_{c} = \frac{L + l_{p}}{v_{f}}

h = \frac{f_{n}}{2} \cdot \sin (σ / 2)

F_{c} = k_{c} \cdot \frac{f_{n}}{2} \cdot \frac{D_{c}}{2}

P_{c} = \frac{F_{c} \cdot v_{c}}{60000} = \frac{f_{n} \cdot v_{c} \cdot D_{c} \cdot k_{c}}{240000}

M_{c} = \frac{F_{c} \cdot D_{c}}{2000}

Fc is the force on one lip. Units: Dc mm, n rpm, vc m/min, fn mm/rev, L and lp mm, vf mm/min, Q cm³/min, kc N/mm², Fc N, Pc kW, Mc N·m.

Notes

vc is the speed at the drill periphery. It falls to zero toward the centre, where the chisel edge extrudes rather than cuts. Real thrust and torque are therefore higher than this model gives.
The force model is for a two-lip drill: each lip cuts a chip fn/2 thick and Dc/2 wide, with a lever of Dc/4. For indexable drills with centre and periphery inserts, use the maker’s formula.
Drilling time includes the point length lp: the tip travels lp before the full diameter reaches the depth. Approach, retract and peck moves are not included.
Pc is the net cutting power. For the motor, divide by the spindle efficiency and check the machine’s power curve against the spindle speed.

Sources (2)

Iscar — Drilling Handbook, formulas page (MRR, net power, torque)
O. Kienzle, VDI-Z 94 (1952) — specific cutting force kc = kc1.1 · h^−mc