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:
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The tabulated recommended tapping speeds should be modified for the following:
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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 |
