Speeds Information
Tapping speeds not only affect productivity, but they can influence the tap
life and the part quality. The feed of a tap cannot be varied independently as
can be done with other cutting tools. The tap feed is fixed by the number of
threads per inch or the lead of the tap threads.
Excessive speed can cause early tap failure due to the high temperature.
Also, failure can be accelerated due to the welding of small particles of the
workpiece material to the tap surfaces. Factors to be considered when
determining the best tapping speed are the following:
- Type of material to be tapped
- Hardness of material to be tapped
- Length or depth of hole
- Whether through or blind hole
- Length of tap chamfer
- Lead of the thread
- Tapping fluid used
- Condition and type of machine
- Percentage of thread to be cut
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The tabulated recommended tapping speeds should be modified for the following:
- Speeds may have to be lowered as the length of hole increases, owing to the
accumulation of chips that increase friction and interfere with lubrication.
- Speeds can be increased when using spiral point, spiral flute, or forming taps.
- Speeds should be decreased when using bottoming taps.
- Speeds can be increased as the percentage of thread is decreased.
- Speeds should be decreased for coarse thread taps.
- Taper pipe taps should be run at between one-half and three-quarters the speed
of a comparable tap of the same diameter and pitch.
- The quantity and quality of tapping fluids may affect the tapping speed significantly.
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The recommended peripheral speeds shown in the following table are only starting points.
| Material |
Speed in feet
per minute (fpm) |
| Aluminum |
50 - 150 |
| Aluminum Bronze |
20 - 80 |
| Brass |
50 - 200 |
| Bronze |
50 - 100 |
| Cast iron |
50 - 100 |
| Copper |
30 - 60 |
| Fiber |
80 - 90 |
| Magnesium |
75 - 200 |
| Malleable Iron |
35 - 60 |
| Monel Metal |
20 - 40 |
| Plastic - thermoplastic |
50 - 100 |
| Plastic - thermosetting |
50 - 100 |
| Steel - free machining |
40 - 80 |
| Stainless steel |
5 - 35 |
| Titanium alloys |
10 - 40 |
| Zinc die casting |
60 - 150 |
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