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 Rc	Speed SFM	Speed RPM
Steel
Mild Steel		155
Plain Carbon		155
Alloyed	<30	130
Alloyed (Hardened & Tempered)	30-38	110
Alloyed (Hardened & Tempered)	38-45	90
Cast Iron
Cast Iron		170
Titanium
Alloys (Annealed)		110
Alloys (Treated), Inconel		60
Aluminum – Magnesium
Aluminum		400
Magnesium		400

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