Trapezoidal thread taps for motion threads
Trapezoidal threads transmit force and motion rather than joining parts: on the spindles of presses, vices, lifting tables and machine tools. Their profile is flatter and carries more load than that of a fastener thread. VÖLKEL makes the matching hand taps in HSS-G from Tr 10 x 2 to Tr 36 x 6, as three-piece sets and as single taps.
Why trapezoidal threads are cut in three stages
The pitch of a trapezoidal thread is large and the profile deep. A single tool would have to remove considerably more material at once than on a coarse thread. The cutting work is therefore spread over three tools: taper tap, second tap and bottoming tap. You can buy the complete set or order single taps when one is worn.
Tapping drill
For a trapezoidal thread the drill size does not follow a simple rule of thumb. Values from the VÖLKEL table:
| Thread | Tapping drill |
|---|---|
| Tr 10 x 2 | 8.2 mm |
| Tr 12 x 3 | 9.25 mm |
| Tr 16 x 4 | 12.25 mm |
| Tr 20 x 4 | 16.25 mm |
| Tr 24 x 5 | 19.25 mm |
| Tr 30 x 6 | 24.25 mm |
| Tr 36 x 6 | 30.25 mm |
The complete series comes with every tool as technical information.
Do not confuse with ACME
The metric trapezoidal thread has a flank angle of 30°, the American ACME thread 29°. The difference is small but enough to make the two incompatible. If you are facing an American spindle, check the angle before reaching for a metric tool.
For series production of trapezoidal nuts there are machine nut taps in Tr versions. Tap wrenches for the large squares are under tool holders.
