Dimensions
| Designation | 1/8-28 BSPP |
|---|---|
| Major (outside) diameter | 9.728 mm · 0.383" |
| Pitch | 0.907 mm · 28 TPI |
| Pitch diameter | 9.139 mm · 0.3598" |
| Minor diameter (external) | 8.615 mm · 0.3392" |
| Minor diameter (internal) | 8.746 mm · 0.3443" |
| Recommended tap drill | — |
BSPP (G) — British parallel pipe
1/8-28 BSPP
1/8-28 BSPP pipe thread: 28 TPI, major Ø 9.728 mm.
Tap drill
—
9.728 mm major Ø
Profile
Thread form & key diameters
What tap drill do I need for 1/8-28 BSPP?
1/8-28 BSPP is a BSPP pipe thread running at 28 threads per inch on a 9.728 mm major diameter. BSPP (G) is a parallel thread sealed by a bonded washer or gasket, not by thread interference — so it has no tapered tap-drill sizing.
All values are generated from the standard thread formulas (ISO 68-1 / ASME B1.1) and published standard tables — not hand-entered. See the full reference.
Same diameter
Other 1/8" BSPP threads
Nearby sizes