Pipe thread database

Fifteen thread standards, one straight answer.

NPT, NPTF, BSPT, BSPP, metric, and every straight and hybrid variant in between -- basic dimensions, a thread profile diagram, and a live tap drill calculator for each. Start with the distinction that actually matters: whether a thread seals on the taper or needs help from something else.

Tapered

Pitch diameter shrinks steadily along the thread, so the joint wedges tighter the further it's driven home -- the seal is the thread engagement itself.

Straight

Pitch diameter holds constant along the full thread length. Any seal has to come from somewhere else: a gasket, a washer, or a mating tapered thread.

Hybrid

Either the joint pairs a straight member against a tapered one, or the thread is fully tapered but built for mechanical strength rather than a pressure-tight seal.

Tapered