Tap 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	50-60
Structural	<200	50-60
Plain Carbon	<250	50-60
Alloyed	<250	32-50
Alloyed (Hardened & Tempered)	250-350	22-32
Alloyed (Hardened & Tempered)	>350	10-16
Stainless Steel
Free Machining	<250	22-32
Austenitic	<250	16-22
Ferritic Austenitic	<300	10-16
Cast Iron
Lamellar Graphite	<150	50-80
Lamellar Graphite	150-300	30-40
Nodular Graphite (Malleable)	<200	30-40
Nodular Graphite (Malleable)	200-300	20-30
Titanium
Unalloyed	<200	32-50
Alloyed	<270	22-40
Alloyed	270-350	16-22
Nickel
Unalloyed	<150	22-40
Alloyed	>270	16-22
Alloyed	270-350	10-16
Copper
Unalloyed	<100	22-40
Brass – Bronze	<200	82-115
Brass	<200	50-65
Bronze High Strength	<470	10-16
Aluminum – Magnesium
Unalloyed	<100	32-50
Silicon Alloyed < 5%	<150	82-150
Silicon Alloyed > 5 < 10%	<120	50-65
Silicon Alloyed > 10%	<120	32-50
Plastic
Thermoplastic	–	60-105
Thermosetting	–	22-40