1 ¼
For 1 ¼, thread standard is BSP; threads per inch (tpi) is 11; major (outside) diameter (mm) is 41.9, recorded from its source on 2026-08-12.
- Thread standard
- BSP our reading
- Nominal size
- 1 ¼ verified
- Threads per inch (TPI)
- 11 verified
- Major (outside) diameter (mm)
- 41.9 verified
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
-20 (1 ¼) | 11 | 41.9 | 1.65 | 39.6 | 1.56
— trimantec.com, retrieved 2026-08-12
Source
- trimantec.comhttps://trimantec.com/blogs/t/thread-identification-guide