BSP (G) male thread envelopes 1/8 to 1 in (ISO 228-1) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/bsp-thread-envelopes/  (CC BY 4.0)
Basis: ISO 228-1 (G, parallel) and ISO 7-1 (R / Rc, taper) BSP major diameters and TPI
Catalog version: 2026-10-20

Sizes: see table below
- Each file is a plain cylinder at the BSPP (G) major OD, 14 mm long, with a 0.8 mm chamfer on the end; the thread form is not modelled.
- Major OD: G1/8 9.73, G1/4 13.16, G3/8 16.66, G1/2 20.96, G3/4 26.44, G1 33.25 mm; 28, 19, 19, 14, 14 and 11 TPI.
- BSP is a 55° thread; parallel G seals on a washer or O-ring, taper R on the thread.
- BSP and NPT do not interchange: 1/2 NPT is 14 TPI 60° and 21.34 OD, G1/2 is 14 TPI 55° and 20.96 OD.

size  od_mm  tpi  file_length_mm
G1/8  9.73  28  14
G1/4  13.16  19  14
G3/8  16.66  19  14
G1/2  20.96  14  14
G3/4  26.44  14  14
G1  33.25  11  14

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Wikipedia: National pipe thread — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/National_pipe_thread
- Wikipedia: British Standard Pipe — web — CC BY-SA 4.0 (text) — https://en.wikipedia.org/wiki/British_Standard_Pipe
- Long Earth Society: Engine builds that use these parts (videos and write-ups) — web, video — LES site — https://longearthsociety.com/engineering/

Free files (CC BY 4.0, Xem Studio; STEP + STL, 6 parts): https://xemstudio.com/files/hardware/bsp-thread-envelopes/index.json
API: https://xemstudio.com/api/geometry?object=bsp-thread-envelopes