Mill Speed is measured by the rate at which the outside diameter of the tool moves in relation to the work piece. This speed is known as Surface Feet Per Minute (SFM) and is shown in the table below. The formula used to convert SFM to Revolutions Per Minute (RPM) is:


The speeds shown in this table are a generalization and it is recommended that the user start at the lower end of the range and build up to the maximum after trial indicates this is possible.

Material	Hardness BHN	Speed SFM	Speed RPM
Steel
Magnetic Soft	<120	92-130
Structural	<200	72-105
Plain Carbon	<250	60-82
Alloyed	<250	60-82
Alloyed (Hardened & Tempered)	250-350	45-65
Alloyed (Hardened & Tempered)	>350	22-40
Stainless Steel
Free Machining	<250	60-82
Austenitic	<250	45-65
Ferritic Austenitic	<300	22-40
Cast Iron
Lamellar Graphite	<150	72-105
Lamellar Graphite	150-300	60-82
Nodular Graphite (Malleable)	<200	72-105
Nodular Graphite (Malleable)	200-300	45-65
Titanium
Unalloyed	<200	72-105
Alloyed	<270	45-65
Alloyed	270-350	22-40
Nickel
Unalloyed	<150	92-130
Alloyed	>270	22-40
Alloyed	270-350	22-32
Copper
Unalloyed	<100	195-260
Brass – Bronze	<200	92-130
Brass	<200	115-165
Bronze High Strength	<470	32-50
Aluminum – Magnesium
Unalloyed	<100	260-330
Silicon Alloyed < 5%	<150	195-260
Silicon Alloyed > 5 < 10%	<120	130-195
Silicon Alloyed > 10%	<120	115-165
Plastique
Thermoplastic	–	195-260
Thermosetting	–	130-195

Recommended Feeds For Milling

Mill Diameter	Slot Drill – Feed per tooth	End Mill – Feed ber tooth
1/16 – 3/32 1/8 – 5/32 3/16 – 7/32 1/4 – 7/16 1/2 – 1" Over 1"	0.0005 0.0007 0.0010 0.0020 0.0030 0.0050	0.0005 – 0.0010 0.0007 – 0.0012 0.0010 – 0.0015 0.0015 – 0.0020 0.0020 – 0.0025 0.0025 – 0.0030