Knuckle thread taps for robust joints
Round threads have rounded crests and roots instead of sharp flanks. That makes them tolerant of dirt, sand and damage, and they still engage when a sharp thread has long since jammed. They sit on fire hose couplings, fittings, railway and mining equipment. VÖLKEL makes the taps to DIN 374 form C in HSSE, from Rd 8 x 1/10 to Rd 44 x 1/6.
Reading the designation
In Rd 20 x 1/8, 20 is the nominal diameter in millimetres and 1/8 gives the pitch as a fraction of an inch. An eighth of an inch is 3.175 mm. That is a historical convention and looks unfamiliar, but it changes nothing about handling. The series uses three pitches: 1/8 inch across the middle range from Rd 14 to Rd 38, 1/10 inch on the small diameters Rd 8 to Rd 12, and 1/6 inch on Rd 40 to Rd 44.
Tapping drill
| Thread | Tapping drill |
|---|---|
| Rd 8 x 1/10 | 6.0 mm |
| Rd 10 x 1/10 | 8.0 mm |
| Rd 12 x 1/10 | 10.0 mm |
| Rd 20 x 1/8 | 17.5 mm |
| Rd 30 x 1/8 | 27.5 mm |
| Rd 40 x 1/6 | 36.6 mm |
| Rd 44 x 1/6 | 40.6 mm |
Form C for blind holes
All versions are form C with right-hand spiral flutes. The chamfer of two to three threads moves the chips back out of the hole, which is the decisive point in a blind hole. HSSE copes with the tough materials in which round threads usually sit.
Other thread systems are under machine taps, checking the finished thread under thread gauges.
All sizes at a glance
21 articles in 1 series. The article number links straight to the tool.
Machine Tap DIN 374 Form C HSSE
| Threadnominal size | Tapping drillØ in mm | Article no. |
|---|---|---|
| Rd 8 x 1/10 | 6 | 79440 |
| Rd 9 x 1/10 | 7 | 79441 |
| Rd 10 x 1/10 | 8 | 79442 |
| Rd 11 x 1/10 | 9 | 79443 |
| Rd 12 x 1/10 | 10 | 79444 |
| Rd 14 x 1/8 | 11.5 | 79445 |
| Rd 16 x 1/8 | 13.5 | 79446 |
| Rd 18 x 1/8 | 15.5 | 79447 |
| Rd 20 x 1/8 | 17.5 | 79448 |
| Rd 22 x 1/8 | 19.5 | 79449 |
| Rd 24 x 1/8 | 21.5 | 79450 |
| Rd 26 x 1/8 | 23.5 | 79451 |
| Rd 28 x 1/8 | 25.5 | 79452 |
| Rd 30 x 1/8 | 27.5 | 79453 |
| Rd 32 x 1/8 | 29.5 | 79454 |
| Rd 34 x 1/8 | 31.5 | 79455 |
| Rd 36 x 1/8 | 33.5 | 79456 |
| Rd 38 x 1/8 | 35.5 | 79457 |
| Rd 40 x 1/6 | 36.6 | 79458 |
| Rd 42 x 1/6 | 38.6 | 79459 |
| Rd 44 x 1/6 | 40.6 | 79460 |
Tapping drill: drill diameter recommended by VÖLKEL (Technical Information “Tapping drill sizes”).
