Cutting Tools Reference Library · Wall Charts

Metric Cutting Speed Chart — m/min to RPM

Spindle speed in RPM for common cutting speeds in meters per minute and metric tool diameters, calculated from n = 1000 × Vc ÷ (π × D).

Ref CT-0057

Draft, open for review. Check every value against the governing standard and the manufacturer’s data before use.

What it is

Metric tool data gives cutting speed (Vc) in meters per minute. The machine needs spindle speed (n) in RPM. The conversion is:

n = (1000 × Vc) ÷ (π × D), or about n = 318.3 × Vc ÷ D
Vc = π × D × n ÷ 1000

D is the tool diameter in millimeters, or the workpiece diameter for turning.

How to use it

Look up the starting Vc for the tool and material in the tool maker's catalog. Find the diameter row and the nearest Vc column. If the machine cannot reach the RPM, run at its maximum and adjust feed to keep the chip load right.

RPM by diameter and cutting speed

Diameter (mm)	20 m/min	50 m/min	100 m/min	150 m/min	200 m/min	300 m/min
2	3,183	7,958	15,915	23,873	31,831	47,746
3	2,122	5,305	10,610	15,915	21,221	31,831
4	1,592	3,979	7,958	11,937	15,915	23,873
5	1,273	3,183	6,366	9,549	12,732	19,099
6	1,061	2,653	5,305	7,958	10,610	15,915
8	796	1,989	3,979	5,968	7,958	11,937
10	637	1,592	3,183	4,775	6,366	9,549
12	531	1,326	2,653	3,979	5,305	7,958
16	398	995	1,989	2,984	3,979	5,968
20	318	796	1,592	2,387	3,183	4,775
25	255	637	1,273	1,910	2,546	3,820
32	199	497	995	1,492	1,989	2,984

Key points

1 m/min is about 3.28 SFM. 100 m/min is about 328 SFM.
Columns can be added: 250 m/min is the 50 m/min value plus the 200 m/min value.
These are calculated values only. The correct Vc depends on tool grade, coating, work material and setup.
Metric feed is usually given as fz (mm per tooth) or f (mm per revolution). Feed rate vf (mm/min) = n × z × fz.

Common mistakes

Entering the radius instead of the diameter.
Mixing an inch diameter with a metric cutting speed.
Running small tools at the calculated RPM on a machine whose spindle cannot hold that speed, then not reducing feed to match.

Governing standards: None. Cutting data comes from the tool manufacturer.

Reference only. Verify against the current governing code or standard, the manufacturer's data and the project documents before use. Apps for Distributors disclaims liability arising from reliance on this reference.

More in Wall Charts

← All Cutting Tools sheets