R1/4 thread: 13.16 mm × 19 TPI
Threads › R1/4
R1/4 is a BSPT taper (R / Rc) thread: 13.16 mm major diameter, 19 TPI (1.337 mm pitch), 55° form. Tap drill 11.2 mm. Taper thread: the Ø changes along the length, measure near the start.
| Standard | BSPT taper (R / Rc) |
|---|---|
| Major diameter | 13.157 mm (0.518″) |
| Pitch | 19 TPI (1.337 mm) |
| Thread angle | 55° |
| Tap drill | 11.2 mm |
Open R1/4 in BenchsmithAdd to order list
Measure it
Bolt: Measure across the crests of the bolt with the caliper jaws. Worn bolts read 0.1 to 0.3 under.
Nut or tapped hole: Measure across the tops of the threads inside the nut or hole with the inside jaws. That is the minor Ø. Worn or oversize holes read a little over.
Close in size, won't mate
- G1/4Ø13.16 mm, 19 TPI
- 1/2-13 UNCØ12.7 mm, 13 TPI
- 1/2-20 UNFØ12.7 mm, 20 TPI
- 1/2 BSWØ12.7 mm, 12 TPI
- 1/2-10 ACMEØ12.7 mm, 10 TPI
- 1/4-18 NPTØ13.72 mm, 18 TPI
One size up or down
Got a bolt and no idea what it is? Measure the outside Ø and type it into Benchsmith → Find → Thread.