Calculator Inputs
Formula Used
The calculator converts all inputs to metric values first. It then applies drilling physics and machine limits.
- RPM:
RPM = 1000 × Vc ÷ (π × D) - Imperial RPM:
RPM = 3.82 × SFM ÷ Diameter - Feed rate:
Feed rate = RPM × Feed per revolution - Chip load:
Chip load = Feed per revolution ÷ Cutting edges - Hole area:
Area = π × D² ÷ 4 - Material removal rate:
MRR = Area × Feed rate - Power:
Power kW = MRR × Kc ÷ 60,000,000 ÷ Efficiency - Torque:
Torque N·m = 9550 × Power kW ÷ RPM - Point length:
Point length = 0.5 × D ÷ tan(Point angle ÷ 2) - Cycle time:
Time = Travel ÷ Feed rate + Peck overhead + Dwell
How to Use This Calculator
- Select metric or imperial units.
- Choose the work material, tool material, and coolant condition.
- Enter drill diameter, hole depth, and number of holes.
- Leave surface speed, feed, and cutting force blank to use presets.
- Enter machine limits when you want RPM, feed, power, or torque checks.
- Use overrides to make conservative or aggressive test settings.
- Press the calculate button.
- Review RPM, feed rate, chip load, power, torque, and cycle time.
- Download the result as CSV or PDF for shop records.
Example Data Table
| Material | Tool | Diameter | Surface Speed | Feed per Rev | Typical Use |
|---|---|---|---|---|---|
| Aluminum 6061 | HSS | 10 mm | 95 m/min | 0.18 mm/rev | Fast drilling with coolant or mist. |
| Mild Steel | HSS | 10 mm | 28 m/min | 0.12 mm/rev | General workshop drilling. |
| Stainless Steel 304 | Cobalt | 8 mm | 18 m/min | 0.08 mm/rev | Controlled heat and steady feed. |
| Cast Iron | Carbide | 12 mm | 24 m/min | 0.14 mm/rev | Dry drilling with chip control. |
| Titanium Grade 5 | Carbide | 6 mm | 12 m/min | 0.06 mm/rev | Low speed and strong coolant flow. |
Drilling Feeds and Speeds Guide
Why Drilling Speed Matters
Drilling is a cutting process. The drill edge removes metal by shearing chips. Speed controls heat at the cutting edge. Feed controls chip thickness. A balanced setting improves hole size, finish, and tool life. Too much speed burns the lips. Too little feed rubs the edge. Both faults waste power and time.
Physics Behind the Cut
A drill creates a circular chip area. The material removal rate equals hole area times feed speed. Specific cutting force converts this removal rate into power. Torque follows from power and spindle speed. These estimates help compare tools, motors, and materials before a part reaches the machine.
Using Practical Limits
Real machines have limits. A small drill may ask for very high RPM. A large drill may need more torque. The calculator caps spindle speed and feed rate when limits are entered. It also compares estimated power and torque with available capacity. This gives a safer starting point for manual mills, drill presses, and CNC machines.
Improving the Result
Use catalog data when possible. Start with conservative values for hard alloys. Increase speed only when chips are clean and temperature stays controlled. Use peck drilling for deep holes. Apply coolant when material sticks or work hardens. Check runout, clamping, and drill condition. These items often matter as much as the formula.
Reading the Outputs
RPM shows spindle speed. Feed rate shows axis travel per minute. Chip load shows feed carried by each cutting edge. Material removal rate shows productivity. Torque and power show mechanical demand. Cycle time estimates production time, including pecks and dwell. Treat the results as a technical starting point, not a guarantee. Test cuts should confirm the final setting.
Safety Notes
Feeds and speeds are not fixed laws. They depend on drill geometry, coating, workholding, coolant, and machine stiffness. Use eye protection. Clear long chips safely. Stop if vibration rises, chips discolor, or the hole squeals. For critical parts, record the final approved setting. That record helps future jobs. It also makes quoting and process planning more consistent. Keep notes on drill wear, burr size, and hole accuracy. Small observations improve the next setup and reduce scrap.
FAQs
1. What is drilling feed rate?
Drilling feed rate is the linear travel of the drill per minute. It depends on spindle RPM and feed per revolution. Higher feed removes material faster, but it also increases torque, thrust, and tool load.
2. What is surface speed in drilling?
Surface speed is the cutting speed at the outside edge of the drill. It is measured in meters per minute or surface feet per minute. It strongly affects heat, wear, and chip formation.
3. Why does drill diameter change RPM?
A larger drill covers more edge distance per revolution. To keep the same surface speed, RPM must decrease as diameter increases. Small drills usually need higher RPM than large drills.
4. Should I always use the calculated RPM?
No. Treat the result as a starting point. Adjust for tool wear, setup rigidity, coolant, hole depth, and chip behavior. Use lower settings for weak machines or difficult materials.
5. What does chip load mean?
Chip load is the feed carried by each cutting edge. It helps show whether the drill is cutting or rubbing. Too little chip load creates heat. Too much chip load can break the tool.
6. Why is peck drilling included?
Peck drilling helps clear chips from deeper holes. It reduces packing, heat, and drill wandering. The calculator adds retract time for each peck to estimate a more realistic cycle time.
7. How is drilling power estimated?
Power is estimated from material removal rate and specific cutting force. The calculator then adjusts for machine efficiency. This gives a useful motor demand estimate, not an exact dynamometer reading.
8. Can this calculator be used for CNC drilling?
Yes. It can estimate CNC drilling RPM, feed rate, chip load, torque, power, and cycle time. Always confirm values with toolmaker recommendations, machine limits, and trial cuts.