Forexample; a 3/4" NPT pipe thread has an outside diameter of 1.050 inches and 14 threads per inch. Each thread size has a defined number of threads per inch (TPI), but Find figure nearest this dimension in column 1 or 2 of chart. The dimension in column 3 will be your nominal pipe thread size. Female Threads: BSPis a British standard for pipe threads defined by ISO 7 & ISO 228. It is the most commonly used pipe thread system outside the USA. In North America, the more popular standard is NPT.. Although it is a British standard and the nominal pipe sizes are in Inches, the dimensions are defined in millimeters. 1200. Metric threads. Minimum modeled diameter (mm) Maximum modeled diameter (mm) 75% hole drill size (mm) Maximum thread depth (mm)*. M1.6 x 0.35**. 1.22. 1.32. 277. 33. General notes.. Dimensions are in millimeters unless otherwise indicated. Dimension ( B) is minimum length of perfect thread. The length of useful thread ( B plus threads with fully formed roots and flat crests) shall not be less than J. safety. Atcertain sizes, NPT and BSP share the same number of threads per inch - at ½" and ¾" - but at all other sizes the two are quite different. The table below lists the TPI for both Forexample, M8 X 0.75 means an 8 mm (0.315″) thread with a pitch of 0.75 mm (0.03″ or 34 TPI). If the “X P” is omitted, the pitch is defined by the Coase Pitch Series according to ISO-261. Number of starts: Designated by “Ph”. For example, M8 X Ph2.25P0.75. In this case, 2.25 mm is the lead, and 0.75 mm is the pitch. Ph must be a ISO228: for joint of external and internal parallel threads (G)/ BSPP. ISO 7 or EN 10226: for external taper (R), internal parallel (Rp) and internal taper (Rc) BSPT. NPT is American Standard Taper Pipe Thread (ANSI/ASME B1.20.1), Taper 1:16. BSPP is totally different from both BSPT and NPT, as it parallel threads. BSP thread dimensions as 226. * Thread size refers to the nominal bore of the pipe. Subtract approx. 1/4″ (6mm) from thread diameter measurement for nominal pipe size. NPT – NPT : NPT to fixed NPT female sealing is made through direct metal to metal contact. The use of Volz Thread Sealant is recommended. NPT – NPSM : NPT male with conical 30° seat (60 milegKk.