Example Data Table
| Material |
Cutting Speed m/min |
Cutting Speed SFM |
Feed mm/rev |
Feed in/rev |
Specific Force N/mm² |
| Mild Steel |
25 |
82 |
0.12 |
0.0047 |
1800 |
| Stainless Steel |
15 |
50 |
0.08 |
0.0031 |
2500 |
| Aluminum |
90 |
295 |
0.18 |
0.0071 |
700 |
| Brass |
60 |
197 |
0.16 |
0.0063 |
900 |
| Cast Iron |
22 |
72 |
0.13 |
0.0051 |
1600 |
| Plastic |
80 |
262 |
0.2 |
0.0079 |
350 |
Formula Used
RPM: RPM = 1000 × Vc ÷ πD, when Vc is in m/min and D is in mm.
Inch RPM: RPM = 3.82 × SFM ÷ diameter in inches.
Feed Rate: feed rate = RPM × feed per revolution.
Feed Per Revolution: feed per revolution = feed per tooth × number of flutes.
Point Allowance: allowance = diameter ÷ 2 ÷ tan(point angle ÷ 2).
Material Removal Rate: MRR = hole area × feed rate.
Power Estimate: power = specific cutting force × MRR ÷ 60000 ÷ efficiency.
Torque: torque = power ÷ angular velocity.
Thrust Estimate: thrust uses diameter, feed, point angle, and cutting force.
How to Use This Calculator
- Select metric or inch units.
- Choose the closest material preset.
- Enter drill diameter and hole depth.
- Add cutting speed and feed, or leave them blank.
- Enter point angle, flutes, and machine RPM limit.
- Press calculate to view results below the header.
- Download the result as CSV or PDF when needed.
Why Drill Speed Matters
Drilling looks simple, yet the physics is active. A rotating edge must shear metal, carry heat, and clear chips. Speed controls surface contact. Feed controls chip thickness. Both choices affect accuracy and tool life.
A small drill can rotate faster than a large drill. The rim travels a shorter path each revolution. A large drill needs lower RPM for the same cutting speed. That is why diameter is part of the main equation.
Feed rate is also important. Too little feed can rub the edge. Rubbing creates heat without making a clean chip. Too much feed can overload the drill. It may bend, chatter, or break.
Physics Behind the Estimate
This calculator links rotational speed, linear feed, and material removal. It also estimates torque, power, point allowance, and drilling time. These values help compare setups before cutting real material.
Specific cutting force is used for power estimates. Harder materials often need higher force. Softer materials need less force, but chip control may still matter. Use the material presets as starting guidance, not as final shop rules.
Coolant, coating, tool geometry, rigidity, and runout can change the answer. A rigid machine can accept more feed. A weak setup may need slower settings. Deep holes often need pecking and coolant flow. Stainless steel may need firm feed to avoid work hardening.
Using Results Safely
Start with the calculated RPM and feed. Then listen to the cut. Smooth chips and stable sound are good signs. Blue chips, squealing, smoke, or heavy vibration mean the setup needs changes.
Use lower speed for poor clamping. Use lower feed for fragile drills. Use peck depth for long holes. Increase coolant when heat rises. Always check machine limits before using the final numbers.
Good drilling practice is a balance. The calculator gives a physics based target. Your machine, tool, and material finish the decision. Record successful settings for future work. A saved record makes repeat jobs faster. It also helps new operators learn from proven values.
For plastics and composites, sharp tools are critical. Heat can melt edges or damage fibers. For cast iron, chip powder can hide wear. For aluminum, chips may weld to the flute without lubrication during longer drilling cycles.
FAQs
What is drill feed rate?
Drill feed rate is the linear travel of the drill per minute. It depends on RPM and feed per revolution. Higher feed cuts faster, but it also increases thrust and tool load.
What is cutting speed?
Cutting speed is the surface speed at the drill edge. It is based on tool diameter and RPM. Large drills need lower RPM to keep the same surface speed.
Why does material change the result?
Each material resists cutting differently. Hard steels need lower speed and more power. Aluminum can use higher speed, but chips may stick without proper lubrication.
Should I use feed per tooth or feed per revolution?
Use feed per revolution when using standard drilling data. Use feed per tooth when your tooling guide lists chip load per cutting lip. The calculator converts it using flute count.
What does point allowance mean?
Point allowance is extra drill travel caused by the conical tip. A sharp point reaches full diameter after traveling some distance. This affects cycle time and blind hole depth.
Is the power estimate exact?
No. Power is an estimate based on material removal and cutting force. Tool coating, coolant, machine rigidity, and edge condition can change the real value.
Why add a machine RPM limit?
A machine may not reach the calculated RPM. The limit field caps the spindle speed. The calculator then recalculates actual cutting speed and feed outputs.
Can this calculator be used for CNC drilling?
Yes. It gives starting values for CNC drilling. Always test the setup, check chip formation, confirm coolant flow, and follow toolmaker recommendations before production cutting.