Dimensions, drill sizes and wrench sizes for 1/2-14 BSPT.
Designation
1/2-14 BSPT
Major (outside) diameter
20.955 mm · 0.825"
Pitch
1.814 mm · 14 TPI
Pitch diameter
19.777 mm · 0.7786"
Minor diameter (external)
18.729 mm · 0.7374"
Minor diameter (internal)
18.991 mm · 0.7477"
Recommended tap drill
18.25 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 1/2-14 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.
1/2-14 BSPT is a BSPT pipe thread running at 14 threads per inch on a 20.955 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 1/2-14 BSPT?
Drill 18.25 mm before tapping 1/2-14 BSPT. BSPT (R) is a 55° Whitworth tapered thread that seals on the flanks.
Is 1/2-14 BSPT a tapered or parallel thread?
1/2-14 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 1/2-14 BSPT have?
1/2-14 BSPT runs at 14 threads per inch, a pitch of 1.814 mm, on a major diameter of 20.955 mm.
Is there a torque spec for 1/2-14 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.