# How to calculate the RPM for a 12 mm mill?

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Hand tools

Below you will find an example of how to calculate the speed of revolution and the feed rate for 12 mm milling cutters. Our cutting tools specialists will be happy to help you calculate the right usage values. # We use the following formula to calculate the desired speed of revolution:

Speed of revolution (n) = Cutting speed (Vc) x 1000 divided by 3,14 x diameter (d), where:
n = the speed of revolution in revolutions per minute,
Vc = cutting speed in meters per minute,
d = diameter in millimetres.

A different cutting speed belongs to every combination of tools and materials. The cutting speed for non-alloy steel < 800 N/mm², for example, is Vc = 23-28 m/min. For this example we will use a cutting speed of 25 m/min.

This would make the speed of revolution n:
n = (25 x 1000) / (3,14 x 12) = 25,000/37,68 = 663 revs/min.

In order to calculate the bench feed for a 12 mm milling cutter, we will use the following formula: Bench feed Bf = Feed per tooth Fz x number of teeth Z x the speed of revolution n.

Two Flute End Mill
Feed per tooth Fz = 0,065 mm
Number of teeth Z = 2
Bench feed Bf = 0,065 x 2 x 663 = 86 mm/min.

Three Flute End Mill
Feed per tooth Fz = 0,065 mm
Number of teeth Z = 3
Bench feed Bf = 0,065 x 3 x 663 = 129 mm/min.

Four Flute End Mill
Feed per tooth Fz = 0,06 mm
Number of teeth Z = 4
Bench feed Bf = 0,06 x 4 x 663 = 159 mm/min.

Please note: reduce feed when drill-cutting.

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