Hong Life CalculatorsUnderstanding the material removal rate calculator — concept and principle
This calculator finds the material removal rate (MRR), the volume of metal cut away per minute, for milling, turning and drilling. It also gives the chip mass per hour from the material density and the time to remove a given volume. Machinists and manufacturing engineers use it to estimate cycle times and spindle power needs.
How it is calculated
Milling: Q = a_e × a_p × v_f
Turning: Q = v_c × 1,000 × f × a_p
Drilling: Q = (π D² ÷ 4) × f × n
- a_e width of cut, a_p depth of cut (mm), v_f table feed (mm/min), v_c cutting speed (m/min), f feed per revolution (mm/rev), D drill diameter (mm), n spindle speed (rpm).
- Q in mm³/min; ÷ 1,000 for cm³/min; ÷ 16,387 for in³/min. Chips (kg/h) = Q (cm³/min) × density × 60 ÷ 1,000.
The principle
Every machining operation removes a cross-section of material and moves it at some rate. In milling, the cutter takes a slot a_e wide and a_p deep, and the table feed moves it forward v_f millimetres each minute. In turning, the chip has an area f × a_p and the surface passes the tool at the cutting speed. In drilling, the whole hole area advances by f each revolution. Multiplying area by speed gives volume per minute.
Worked example
Default inputs: milling, a_e = 10 mm, a_p = 5 mm, v_f = 500 mm/min, density 7.85 g/cm³, volume 100 cm³.
- Q = 10 × 5 × 500 = 25,000 mm³/min = 25 cm³/min.
- In inches: 25,000 ÷ 16,387 = 1.526 in³/min.
- Chips = 25 × 7.85 × 60 ÷ 1,000 = 11.775 kg/h.
- Time to remove 100 cm³ = 100 ÷ 25 = 4 min.
| Width of cut ae (mm) — milling | Material removal rate (cm³/min) |
|---|---|
| 2.5 | 6.25 |
| 5 | 12.5 |
| 7.5 | 18.75 |
| 10 | 25 |
| 12.5 | 31.25 |
| 15 | 37.5 |
| 20 | 50 |
How to read the result
Higher MRR means shorter machining time but more cutting force, heat and spindle power. Multiplying MRR by the material's specific cutting energy estimates the power needed. Roughing aims for high MRR; finishing passes use low MRR for accuracy and surface finish.
Common mistakes
- Using feed per tooth instead of table feed in milling.
- Forgetting the ×1,000 conversion of cutting speed from m/min to mm/min in turning.
- Comparing MRR without considering tool life and machine power.
Frequently asked questions
How do I estimate spindle power from MRR?
Multiply MRR by the specific cutting energy of the material, taken from machining handbooks or tool makers.
What is table feed in milling?
Feed per tooth × number of teeth × spindle speed.
Why does drilling MRR use the full hole area?
The drill removes the whole circular cross-section as it advances.
How much is 1 in³?
16,387.064 mm³ exactly.
Sources: Standard machining relations for MRR in milling, turning and drilling; 1 in³ = 16,387.064 mm³ (exact)