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Sizes · Pipe (NPT / BSPT / BSPP)

BSPT (R) — British tapered pipe

1/8-28 BSPT

1/8-28 BSPT pipe thread: 28 TPI, major Ø 9.728 mm.

Tap-drill calculatorIdentify a thread
Tap drill
8.4 mm
9.728 mm major Ø

Profile

Thread form & key diameters

Major Ø 9.728 mmP 0.907 mm55°Root Ø 8.615 mm · Pitch Ø 9.139 mm1/8-28 BSPT28 TPI · 55° form

Dimensions

Designation1/8-28 BSPT
Major (outside) diameter9.728 mm · 0.383"
Pitch0.907 mm · 28 TPI
Pitch diameter9.139 mm · 0.3598"
Minor diameter (external)8.615 mm · 0.3392"
Minor diameter (internal)8.746 mm · 0.3443"
Recommended tap drill8.4 mm

What tap drill do I need for 1/8-28 BSPT?

1/8-28 BSPT is a BSPT pipe thread running at 28 threads per inch on a 9.728 mm major diameter. BSPT (R) is a 55° Whitworth tapered thread that seals on the flanks.

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" BSPT threads

1/8-28 BSPPTap —Ø 9.728 mm · pitch 0.907 mm

Nearby sizes

More bspt (r) — british tapered pipe threads

1/4-19 BSPTTap 11.2 mmØ 13.157 mm · pitch 1.337 mm3/8-19 BSPTTap 14.75 mmØ 16.662 mm · pitch 1.337 mm1/2-14 BSPTTap 18.25 mmØ 20.955 mm · pitch 1.814 mm3/4-14 BSPTTap 23.75 mmØ 26.441 mm · pitch 1.814 mm1-11 BSPTTap 30 mmØ 33.249 mm · pitch 2.309 mm1-1/4-11 BSPTTap 38.75 mmØ 41.91 mm · pitch 2.309 mm1-1/2-11 BSPTTap 44.5 mmØ 47.803 mm · pitch 2.309 mm2-11 BSPTTap 56.5 mmØ 59.614 mm · pitch 2.309 mm