Spindle Speed (RPM) Calculator for Turning
Optimize your machining processes with our online cutting parameters calculator. Select the operation type (turning, milling, drilling or threading) and instantly get the critical calculations for your shop: cutting speed (Vc), revolutions per minute (RPM), feed per revolution or per tooth, machining time and the theoretical roughness (Ra / Rz) based on the insert nose radius. To fine-tune those values live at the machine, use the interactive machining calculator.
Cutting calculator
Which operation are you machining?
What do you want to calculate?
Introduce Vc y diámetro
Formula
Result
RPM calculadas
0rpm
Where Vc is the cutting speed in m/min and D is the diameter of the piece, milling cutter or drill bit in millimeters (mm).
Material, power and warnings
Pick material and tool: that gives you the Vc and feed ranges, and also whether your machine can take the cut.
Power, torque and warnings
RPM and feed only tell you how fast it spins. This tells you whether your machine can take it: metal removal rate, the power you have to ask of the spindle, torque and the process warnings that usually cost you a tool.
Pick a material above to estimate power: the specific cutting force depends on it.
Fill in material, diameter, Vc/RPM and feed to see the power.
Rough estimate: kc1.1 is defined per material family and the tool's real geometry matters. Use it to decide whether a cut fits the machine, not as a substitute for a dry run.
Do you want to adjust these values live?
Here you get the recommendation (Vc, feed, roughness, threading). In the interactive machining calculator you can move Vc, diameter, RPM and feed with linked scales, locks and time/power estimation.
Open interactive calculator →Spindle speed in turning: formula, example and table
n = 1000 × Vc / (π × D)
Vc is the cutting speed in m/min, D the part diameter in mm and n the spindle speed in rpm. In turning the diameter that counts is the part diameter being cut, so the speed changes on every pass unless you use constant surface speed (G96).
Worked example: Medium-carbon steel C45 / 1045 in turning, Ø50 mm, Vc 230 m/min → n = 1000 × 230 / (π × 50) = 1464 rpm.
With G97 the rpm are fixed and the real Vc drops as the diameter shrinks: useful for threading, drilling on the centreline or off-centre parts. On small parts the machine often hits its rpm limit before the recommended Vc; then the limit rules, not the table.
| Material | Vc (m/min) | n Ø20 (rpm) | n Ø50 (rpm) | n Ø100 (rpm) |
|---|---|---|---|---|
| Low-carbon steel S235 / St37 | 275 | 4377 | 1751 | 875 |
| Medium-carbon steel C45 / 1045 | 230 | 3661 | 1464 | 732 |
| Alloy steel 42CrMo4 / 4140 | 195 | 3104 | 1241 | 621 |
| 16MnCr5 carburizing steel | 205 | 3263 | 1305 | 653 |
| Austenitic stainless 304 / 1.4301 | 160 | 2546 | 1019 | 509 |
| Austenitic stainless 316 / 1.4401 | 140 | 2228 | 891 | 446 |
| Martensitic stainless 420 / 1.4021 | 145 | 2308 | 923 | 462 |
| Gray cast iron GG25 / EN-GJL-250 | 200 | 3183 | 1273 | 637 |
| GGG50/EN-GJS-500 nodular cast iron | 175 | 2785 | 1114 | 557 |
| Aluminum 6082 / AlMgSi1 | 700 | 11141 | 4456 | 2228 |
| Aluminum 7075 / AlZnMgCu | 625 | 9947 | 3979 | 1989 |
| Brass CuZn39Pb3 | 350 | 5570 | 2228 | 1114 |
| Titanium Ti6Al4V | 60 | 955 | 382 | 191 |
| Inconel 718 | 35 | 557 | 223 | 111 |
| Hardened steel 50-55 HRC | 115 | 1830 | 732 | 366 |
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