ThreadRef

Sizes · Pipe (NPT / BSPT / BSPP)

BSPP (G) — British parallel pipe

1/4-19 BSPP

1/4-19 BSPP pipe thread: 19 TPI, major Ø 13.157 mm.

Tap-drill calculatorIdentify a thread
Tap drill
—
13.157 mm major Ø

Profile

Thread form & key diameters

Major Ø 13.157 mmP 1.337 mm55°Root Ø 11.517 mm · Pitch Ø 12.289 mm1/4-19 BSPP19 TPI · 55° form

Dimensions

Designation1/4-19 BSPP
Major (outside) diameter13.157 mm · 0.518"
Pitch1.337 mm · 19 TPI
Pitch diameter12.289 mm · 0.4838"
Minor diameter (external)11.517 mm · 0.4534"
Minor diameter (internal)11.71 mm · 0.461"
Recommended tap drill—

What tap drill do I need for 1/4-19 BSPP?

1/4-19 BSPP is a BSPP pipe thread running at 19 threads per inch on a 13.157 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 1/4" BSPP threads

1/4-19 BSPTTap 11.2 mmØ 13.157 mm · pitch 1.337 mm

Nearby sizes

More bspp (g) — british parallel pipe threads

1/8-28 BSPPTap —Ø 9.728 mm · pitch 0.907 mm3/8-19 BSPPTap —Ø 16.662 mm · pitch 1.337 mm1/2-14 BSPPTap —Ø 20.955 mm · pitch 1.814 mm3/4-14 BSPPTap —Ø 26.441 mm · pitch 1.814 mm1-11 BSPPTap —Ø 33.249 mm · pitch 2.309 mm1-1/4-11 BSPPTap —Ø 41.91 mm · pitch 2.309 mm1-1/2-11 BSPPTap —Ø 47.803 mm · pitch 2.309 mm2-11 BSPPTap —Ø 59.614 mm · pitch 2.309 mm