1/8
For 1/8, thread standard is BSP; threads per inch (tpi) is 28; thread pitch (mm) is 0.907; major (outside) diameter (mm) is 9.728; minor diameter (mm) is 8.566, recorded from its source on 2026-08-12.
- Thread standard
- BSP our reading
- Nominal size
- 1/8 verified
- Threads per inch (TPI)
- 28 verified
- Thread pitch (mm)
- 0.907 verified
- Major (outside) diameter (mm)
- 9.728 verified
- Minor diameter (mm)
- 8.566 verified
- Thread angle (degrees)
- 55 our reading
- Governing standard
- ISO 228-1 our reading
Values marked our reading are our classification of what the source says — the source does not print them in those words. The quote below is the evidence for each one; judge it yourself.
What the source says
1/8 | 28 | 0.907 | 0.581 | 9.728 | 9.147 | 8.566 |
— amesweb.info, retrieved 2026-08-12
Sources disagree
More than one authority states this, and they do not state the same thing. Both are reproduced with the source each came from — deciding between them is yours, not ours.
Major (outside) diameter (mm)
amesweb.info says major (outside) diameter (mm) is 9.728, as of 2026-08-12.
1/8 | 28 | 0.907 | 0.581 | 9.728 | 9.147 | 8.566 |
https://amesweb.info/Screws/BSP-Thread-Chart.aspx
geminivalve.com says major (outside) diameter (mm) is 9.728, as of 2026-08-12.
1/8 | 28 | 0.0357 | 0.907 | 0.383 | 9.728 | 0.3372 | 8.565 | 0.1563 | 3.97
https://www.geminivalve.com/bsp-thread-vs-npt-fitting/
htsspares.com says major (outside) diameter (mm) is 9.52, as of 2026-08-12.
1/8 Inch BSP | 9.52 mm / 3/8" | 28
https://www.htsspares.com/blog/how-to/how-to-measure-your-bsp-fittings
trimantec.com says major (outside) diameter (mm) is 9.7, as of 2026-08-12.
-02 (1/8) | 28 | 9.7 | 0.38 | 8.9 | 0.35
https://trimantec.com/blogs/t/thread-identification-guide
Minor diameter (mm)
amesweb.info says minor diameter (mm) is 8.566, as of 2026-08-12.
1/8 | 28 | 0.907 | 0.581 | 9.728 | 9.147 | 8.566 |
https://amesweb.info/Screws/BSP-Thread-Chart.aspx
geminivalve.com says minor diameter (mm) is 8.565, as of 2026-08-12.
1/8 | 28 | 0.0357 | 0.907 | 0.383 | 9.728 | 0.3372 | 8.565 | 0.1563 | 3.97
Sources
- amesweb.infohttps://amesweb.info/Screws/BSP-Thread-Chart.aspx
- geminivalve.comhttps://www.geminivalve.com/bsp-thread-vs-npt-fitting/
- htsspares.comhttps://www.htsspares.com/blog/how-to/how-to-measure-your-bsp-fittings
- trimantec.comhttps://trimantec.com/blogs/t/thread-identification-guide