Example Data Table
| Material | D (mm) | f (mm/rev) | RPM | Factor | Thrust (N) | Torque (N·m) | Power (W) |
|---|---|---|---|---|---|---|---|
| Aluminum | 10 | 0.25 | 1800 | 0.94 | 705 | 2.820 | 532 |
| Mild Steel | 8 | 0.18 | 1200 | 1.00 | 1152 | 4.032 | 507 |
| Stainless Steel | 12 | 0.20 | 800 | 1.07 | 2825 | 13.867 | 1162 |
| Cast Iron | 6 | 0.12 | 1400 | 0.98 | 635 | 1.609 | 236 |
| Brass | 14 | 0.22 | 900 | 0.93 | 1289 | 7.218 | 680 |
| Titanium | 5 | 0.08 | 700 | 1.12 | 627 | 1.344 | 99 |
Example values are illustrative and assume typical preset coefficients and modest correction factors.
Formula Used
This calculator uses a practical empirical model that relates drilling loads to drill size and feed.
- Cutting speed: Vc = π·D·n / 1000 (m/min), with D in mm and n in RPM.
- Feed rate: Vf = f·n (mm/min).
- Thrust force: F = Kf·D·f·factor (N).
- Torque: T = Kt·D²·f·factor (N·mm), converted to N·m.
- Spindle power: P = 2π·n·T / 60 (W).
The combined factor multiplies coating, cooling, point, and wear effects to help compare scenarios.
How to Use This Calculator
- Select a material preset, or choose Custom for your own coefficients.
- Enter drill diameter and feed per revolution.
- Pick RPM mode or cutting-speed mode, then enter that value.
- Adjust coating, cooling, point, and wear factors if needed.
- Click Calculate to view thrust, torque, and power values.
- Use Download CSV or Download PDF to save results.
Drilling Force Guide
1) Why thrust and torque matter
Drilling creates two main loads: axial thrust (N) and torque (N·m). High thrust can deflect thin parts, enlarge holes, or slip clamps. High torque raises power demand and can twist small tools. A 10 mm drill in steel can exceed 1,000 N thrust at moderate feeds.
2) Inputs that drive drilling loads
This calculator treats diameter D (mm) and feed per revolution f (mm/rev) as primary drivers. In the model, thrust scales with D·f and torque scales with D²·f. Doubling diameter roughly doubles thrust, but increases torque about four times.
3) Coefficients Kf and Kt by material
Kf and Kt summarize how resistant a material is to drilling. Typical preset values here are about 300/120 for aluminum, 800/350 for mild steel, 1100/450 for stainless, and 1400/600 for titanium (units N/mm²). Choose Custom if you have shop-specific coefficients.
4) Correction factors you can tune
Coating and coolant reduce friction and heat. Example factors are 0.95 for TiN, 0.92 for TiAlN, and 0.94 for flood coolant. Point and wear factors model geometry and tool condition: a sharp split-point may use 0.90–0.98, while a worn edge can push 1.20–1.60. Combined factor multiplies these effects; values from 0.85 to 1.25 are common when comparing sharp, lubricated drills against worn, dry setups.
5) Speed, feed rate, and MRR
If you enter RPM, cutting speed is Vc = π·D·n/1000 (m/min). Feed rate becomes Vf = f·n (mm/min). Material removal rate is area·Vf, where area = π·D²/4. Increasing RPM raises Vf and MRR, but thrust and torque change little in this model.
6) Torque to power and motor sizing
Spindle power uses P = 2π·n·T/60 (W). Example: 4.0 N·m at 1,200 RPM is about 503 W at the spindle. With 0.85 efficiency, motor power is roughly 592 W. Use this check when drilling tougher alloys.
7) Practical planning tips and limits
Start with conservative feeds such as 0.08–0.18 mm/rev for small drills and harder alloys, then step up while watching chip evacuation. If predicted thrust is high, reduce f, improve lubrication, or pilot drill. Real forces vary with runout, rigidity, pecking, and hole depth, so validate with trials.
FAQs
1) What do Kf and Kt represent?
Kf estimates axial thrust per unit D·f, while Kt estimates torque per unit D²·f. They bundle material behavior, tool geometry, and cutting conditions into practical coefficients for planning.
2) Why does torque rise so fast with diameter?
Torque depends on cutting force acting at a radius. As diameter increases, both contact area and lever arm increase, so a D² relationship is a useful planning approximation for similar feeds and materials.
3) Which speed mode should I use?
Use RPM mode if your machine has a fixed spindle speed. Use cutting-speed mode when you follow a tooling chart in m/min. The calculator converts between them using drill diameter.
4) How should I pick point and wear factors?
Start at 1.00. Use 0.90–0.98 for sharp split-points or optimized geometry, and 1.20–1.60 for noticeably worn edges, chatter, or poor chip evacuation.
5) Does increasing RPM change thrust and torque?
In this model, thrust and torque mainly depend on D and f, not RPM. Higher RPM increases feed rate and power because power scales with RPM times torque.
6) Is the motor power output conservative?
Motor power is spindle power divided by efficiency. If you are unsure, use a lower efficiency such as 0.75–0.85 to add margin, then confirm with test cuts and machine load meters.
Note: Real drilling forces depend on tool geometry, runout, hole depth, rigidity, and chip evacuation. Use this tool for planning, comparisons, and sanity checks.