27-01-2019, 08:58 AM
For the amateur few things were less adequately explained than pipe threads, and not overly clear even on the Internet. Few have an assortment of taps and dies to compare. There are taper (BSPT) (NPT) and parallel threads (BSPP) (NPS). A hunt through the data reveals the latter based on some medium point of the taper configuration. The exact designations not consistent down the ages. BP have Whitworth thread form; the NP American form and in some sizes different pitches.
Parallel of a sort can be cut with a two piece taper die suitably maladjusted.
Here for plumbing the BSP series is retained but given metric names!
The size in inches is as for an external thread with designated nominal size that of the bore in original thick walled 19th Century wrought iron pipe. Hence all threads are much larger dia than most expect.
Old die sets and taps can be picked up very cheap and are often handy for making or repairing things needing a large thread. Other large taps and dies tend to be expensive.
Parallel of a sort can be cut with a two piece taper die suitably maladjusted.
Here for plumbing the BSP series is retained but given metric names!
The size in inches is as for an external thread with designated nominal size that of the bore in original thick walled 19th Century wrought iron pipe. Hence all threads are much larger dia than most expect.
Old die sets and taps can be picked up very cheap and are often handy for making or repairing things needing a large thread. Other large taps and dies tend to be expensive.