BSPT (R) - British tapered pipe

1/4-19 BSPT

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

Tap drill
11.2 mm
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 BSPT19 TPI · 55° form

Dimensions

Dimensions, drill sizes and wrench sizes for 1/4-19 BSPT.
Designation1/4-19 BSPT
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 drill11.2 mm

Tightening torque estimate

Pipe threads are made up to a seal against the mating flanks, not tightened to a bolt preload, so no proof load or tightening-torque figure applies.

Put 1/4-19 BSPT on a job sheet

The bolt schedule collects the fasteners for one job onto a single sheet - tap drill, wrench size, grade and tightening torque on every line, taken straight from pages like this one. Free schedules hold 3 lines and are saved in this browser only.

Open bolt schedule

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

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

Frequently asked questions

What drill size do I need to tap 1/4-19 BSPT?

Drill 11.2 mm before tapping 1/4-19 BSPT. BSPT (R) is a 55° Whitworth tapered thread that seals on the flanks.

Is 1/4-19 BSPT a tapered or parallel thread?

1/4-19 BSPT is tapered. BSPT (R) is a 55° Whitworth tapered thread that seals as the flanks wedge together, normally with thread sealant or PTFE tape.

How many threads per inch does 1/4-19 BSPT have?

1/4-19 BSPT runs at 19 threads per inch, a pitch of 1.337 mm, on a major diameter of 13.157 mm.

Is there a torque spec for 1/4-19 BSPT?

No. Pipe threads are made up to a seal against the mating flanks, not tightened to a bolt preload, so no proof load or tightening-torque figure applies.

Same diameter

Other 1/4" BSPT threads

The pipe this thread runs on

NPS 1/4 pipe

NPS 1/4 pipe is 0.54 in across the outside whatever the schedule; at standard wall (std) the wall is 0.088 in and the bore 0.364 in.

Full dimensions for the standard wall · every schedule in the chart

Nearby sizes

More bspt (r) - british tapered pipe threads