BSPT thread, nominal size 1/8 — dimensions

For BSPT thread, nominal size 1/8, threads per inch (tpi) is 28; thread pitch (mm) is 0.907; major (outside) diameter (mm) is 9.73; minor diameter (mm) is 8.57; thread angle (degrees) is 55; governing standard is ISO 7-1, recorded from its source on 2026-08-12.

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

111.55 | 110.07 | 0 | -999.00 | R | <https://www.machiningdoctor.com/threadinfo-bspt/?tid=4513> BSPT R 5 | 5" | 11 | 2.309 | 28.6 | 1.5 / 3.5 | 138.43 | 136.95 | 135.47 | 0 | -999.00 | R | <https://www.machiningdoctor.com/threadinfo-bspt/?tid=4514> BSPT R 6 | 6" | 11 | 2.309 | 28.6 | 1.5 / 3.5 | 163.83 | 162.35 | 160.87 | 0 | -999.00 | BSPT Rc (Internal Tapered) Dimensions Chart Dimensions are in millimeters. To view Inch values, click the Thread Description. The below chart shows only the main dimensions. To view all the dimensions, click the thread description or use the <https://www.machiningdoctor.com/calculators/threading/?fam=BSPT&ser=Rc> BSPT Thread Calculator . series | Thread | Pipe OD | TPI | Pitch | Gauge Length | Tol (Turns/mm) | Major Diam | Pitch Diam | Minor Diam | Fit Allowance (Turns/mm) | Tap Drill Size | Rc | <https://www.machiningdoctor.com/threadinfo-bspt/?tid=4515> BSPT Rc 1/16 | 1/16" | 28 | 0.907 | 4.0 | 1.25 / 1.1 | 7.72 | 7.14 | 6.56 | 0 | 6.4 | Rc | <https://www.machiningdoctor.com/threadinfo-bspt/?tid=4516> BSPT Rc 1/8 | 1/8" | 28 | 0.907 | 4.0 | 1.25 / 1.1 | 9.73 | 9.15 | 8.57 |

— machiningdoctor.com, retrieved 2026-08-12

Source

• machiningdoctor.comhttps://www.machiningdoctor.com/charts/bsp/

Last verified against source: 2026-08-12. Due for re-check by 2028-08-11. This page as Markdown · OKF bundle · full dataset as JSON.