Rc (BSPT): the British tapered pipe thread
Rc is the tapered internal form of the British pipe thread. It belongs to the R external thread and seals on the flanks like NPT, only with a 55° flank angle instead of 60°. In Europe this is the common pipe connection in heating, plumbing, compressed air and hydraulics. VÖLKEL makes 48 versions from Rc 1/16 x 28 to Rc 2.1/2 x 11, to DIN 374 form C in HSSE, as finishing taps to ISO 529 form C in HSS-G, and to JIS B-4430 in form B and form C.
Telling R, Rc, Rp and G apart
- R: tapered external thread.
- Rc: tapered internal thread. R with Rc seals on the flanks.
- Rp: parallel internal thread. R with Rp also seals, but is more often used with a sealant.
- G: parallel, and it does not seal on the thread but on a sealing face or a ring.
All four use a 55° flank angle and the same thread count per nominal size, so some of them can be combined. With American NPT that is not possible. The relationships are covered in the article pipe thread types explained.
The designation is misleading
In Rc 1/2 x 14, the 1/2 is not the outside diameter but the historic nominal bore of the pipe. The thread outside diameter is about 20.9 mm. Anyone searching a table by measured diameter will find nothing that fits.
While cutting
As with any tapered thread, torque rises with depth. Cut to the standard engagement depth, not to a stop. The parallel G versions are under G (BSP) pipe thread, the American variant under NPT, matching gauges under thread plug gauges G (BSP).
All sizes at a glance
48 articles in 3 series. The article number links straight to the tool.
Machine Tap JIS B-4430
| Threadnominal size | Form B HSSE | Form C HSS-G | Form C 35° Spiral Flute HSSE |
|---|---|---|---|
| Rc (BSPT) 1/16 x 28 | 97502 | 97402 | 97702 |
| Rc (BSPT) 1/8 x 28 | 97506 | 97406 | 97706 |
| Rc (BSPT) 1/4 x 19 | 97514 | 97414 | 97714 |
| Rc (BSPT) 3/8 x 19 | 97518 | 97418 | 97718 |
| Rc (BSPT) 1/2 x 14 | 97522 | 97422 | 97722 |
| Rc (BSPT) 3/4 x 14 | 97530 | 97430 | 97730 |
| Rc (BSPT) 1" x 11 | 97538 | 97438 | 97738 |
| Rc (BSPT) 1.1/4 x 11 | 97546 | 97446 | 97746 |
| Rc (BSPT) 1.1/2 x 11 | 97554 | 97454 | 97754 |
| Rc (BSPT) 2" x 11 | 97570 | 97470 | 97770 |
Machine Tap Bottoming ISO 529 Form C HSS-G
| Threadnominal size | Article no. |
|---|---|
| Rc (BSPT) 1/8 x 28 | 87412 |
| Rc (BSPT) 1/4 x 19 | 87414 |
| Rc (BSPT) 3/8 x 19 | 87416 |
| Rc (BSPT) 1/2 x 14 | 87418 |
| Rc (BSPT) 5/8 x 14 | 87419 |
| Rc (BSPT) 3/4 x 14 | 87422 |
| Rc (BSPT) 7/8 x 14 | 87423 |
| Rc (BSPT) 1" x 11 | 87426 |
| Rc (BSPT) 1.1/4 x 11 | 87434 |
| Rc (BSPT) 1.1/2 x 11 | 87442 |
| Rc (BSPT) 2" x 11 | 87454 |
| Rc (BSPT) 2.1/2 x 11 | 87464 |
