Taps for parallel pipe threads
The G thread to BSP is the European pipe thread: parallel, with a flank angle of 55° and rounded crests. It does not seal on the thread itself but on a sealing face or a ring. VÖLKEL makes the machine taps for it to DIN 5156 in form C from HSSE, TiN-coated on request, from G 1/8 x 28 upwards.
Telling G, R and NPT apart
These three are confused most often, and no combination of them can be screwed together:
- G (BSP): parallel, 55°, seals on a face or a ring.
- R external and Rc internal (BSPT): tapered, 55°, seals on the flanks.
- NPT: tapered, 60°, American standard, usually with a sealant.
A G internal thread and an R external thread can be combined when the joint seals on a ring. The relationships are explained in Thread types explained.
The designation
In G 1/2 x 14, 1/2 is not the outside diameter but the inherited nominal bore of the pipe. The actual thread outside diameter is around 20.9 mm. 14 is the number of threads per inch. Anyone measuring the diameter and searching a metric table therefore finds nothing that fits.
Form C and coating
Form C with right-hand spiral flutes moves the chips back and suits through and blind holes. HSSE covers alloyed and stainless steels; the TiN coating raises hardness and tool life and allows higher cutting speeds, as set out in Coatings at a glance.
Tapered pipe threads and other systems are under machine taps, external threads are cut with round dies, checking is done with gauges from the thread gauges.
