How to use this calculator
- Enter drill diameter and RPM. Use the actual cutting diameter and planned spindle speed.
- Enter feed per revolution. Use the axial advance per spindle revolution from the tooling recommendation.
- Enter kc and efficiency. Use material/tool specific cutting force and a machine efficiency allowance.
- Check spindle load. Compare power and torque with the machine spindle curve and load meter.
How it works
Drilling feed rate is feed per revolution multiplied by spindle speed:
Vf = fn x n
Material removal rate uses the drill cross-section area:
Q = (pi x D^2 / 4) x Vf
With kc in N/mm^2 and Q in
mm^3/min, cutting power is:
Pcut(kW) = kc x Q / 60,000,000
Pspindle = Pcut / eta
T = 9550 x Pspindle / n
Worked example
Verified against the live calculator
A 10 mm drill at 1200 rpm and
0.08 mm/rev feed removes about 7.54 cm^3/min.
With kc = 1500 N/mm^2, cutting power is about
0.188 kW. At 80% machine efficiency, required
spindle power is about 0.236 kW.
Frequently asked questions
How do you calculate drilling horsepower?
Calculate drilling feed rate from feed per revolution times RPM, then MRR from drill area times feed rate. Cutting power is estimated from specific cutting force and MRR, then divided by machine efficiency for required spindle power.
Is drilling horsepower the same as milling horsepower?
The power relation is similar, but drilling MRR uses the full drill cross-section area times axial feed rate. Milling MRR uses width of cut, depth of cut and table feed.
What kc value should I use?
Use tooling or material data when available. Specific cutting force changes with material, drill geometry, chip thickness, coating, coolant, web thinning and wear.
Does this include peck drilling or tool changes?
No. This is a spindle-load screen. Cycle time, peck retracts, chip clearing and handling are covered by separate process planning.
Method & assumptions
- Uses solid-drilling MRR: drill area x axial feed rate.
- Specific cutting force is user-entered; use drillmaker or toolmaker data when available.
- Does not model thrust force, web thinning, margin friction, hole depth ratio, chip evacuation, peck cycles, coolant, runout or drill wear.
- Use drilling feed rate, SFM to RPM, milling horsepower and turning horsepower for adjacent checks.