# 3 — Plumbing fitting and pipe thread standards

For 3, thread standard is BSP; threads per inch (tpi) is 11; thread pitch (mm) is 2.309; major (outside) diameter (mm) is 87.884; minor diameter (mm) is 84.926, recorded from its source on 2026-08-12.

- **Thread standard:** BSP _(our reading, not quoted from the source)_
- **Nominal size:** 3 _(verified: appears in the quote below)_
- **Threads per inch (TPI):** 11 _(verified: appears in the quote below)_
- **Thread pitch (mm):** 2.309 _(verified: appears in the quote below)_
- **Major (outside) diameter (mm):** 87.884 _(verified: appears in the quote below)_
- **Minor diameter (mm):** 84.926 _(verified: appears in the quote below)_
- **Thread angle (degrees):** 55 _(our reading, not quoted from the source)_
- **Governing standard:** ISO 228-1 _(our reading, not quoted from the source)_

## What the source says

> 3 | 11 | 2.309 | 1.479 | 87.884 | 86.405 | 84.926 |

## 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.

### Minor diameter (mm)

amesweb.info says minor diameter (mm) is **84.926**, as of 2026-08-12.

> 3 | 11 | 2.309 | 1.479 | 87.884 | 86.405 | 84.926 |

Source: https://amesweb.info/Screws/BSP-Thread-Chart.aspx

geminivalve.com says minor diameter (mm) is **84.927**, as of 2026-08-12.

> 3 | 11 | 0.0909 | 2.309 | 3.46 | 87.884 | 3.3436 | 84.927 | 0.8125 | 20.638

Source: https://www.geminivalve.com/bsp-thread-vs-npt-fitting/


## Source

- https://amesweb.info/Screws/BSP-Thread-Chart.aspx
- https://www.geminivalve.com/bsp-thread-vs-npt-fitting/

Last verified: 2026-08-12. Review by: 2028-08-11.
Part of [Plumbing fitting and pipe thread standards](https://referencesource.org/plumbing-fitting-thread-standards/).