How to use the Cutting Speed and Machining Time Calculator
- 1. Pick the operationTurning, drilling or milling, and whether you know V or rpm.
- 2. Enter cut dataDiameter, feed, depth of cut, length of cut and approach.
- 3. Get the timerpm, cutting speed, feed rate, time, MRR and (optional) power.
Machining formulas
- Cutting speed V = πDN / 1000 m/min, so N = 1000V / (πD).
- Turning: time per pass = (L + approach) / (f·N), MRR ≈ π(D − d)·d·f·N.
- Drilling: point allowance = (D/2) / tan(point angle/2), which is about 0.3D for 118°. Time = (depth + allowance + approach) / (f·N).
- Milling: table feed vf = fz·z·N. Slab milling approach = √(d(D − d)); with a centred face cutter, add D. MRR = width × depth × vf.
- Cutting power = MRR × specific cutting energy.
Cutting speeds and specific energies depend on the tool and work material. The defaults are examples; use your tool maker's data or your question.
Worked example and exam tips
A 50 mm bar is turned at 30 m/min with a feed of 0.2 mm/rev over a 200 mm length. N = 1000 × 30 / (π × 50) = 191 rpm. Time per pass = 200 / (0.2 × 191) = 5.24 min. With 5 mm of approach and overtravel, it becomes 5.37 min.
- Use the larger diameter for V in turning. Set the machine to the nearest available rpm below the calculated value.
- Number of passes = total depth / depth per pass, rounded up.
- Do not forget the approach length in milling. It is often asked in exams.
Frequently asked questions
Why is cutting speed given in m/min?
Tool life depends on the speed of the cutting edge over the work surface. Using m/min lets one value work for any diameter.
What is a good cutting speed?
It depends on the tool and work material. HSS on mild steel is often run at about 25 to 30 m/min and carbide much faster. Check your tool data.
Does machining time include setup?
No. It is cutting time only. Add loading, setup, tool change and inspection time to get the full job time.
Is this calculator free?
Yes. You fill in a short form once to see your result, and the other Uncodemy tools then open without it. Every calculation runs in your browser and nothing you type is sent anywhere.