3/4 BSW thread: 19.05 mm × 10 TPI

Threads › 3/4 BSW

3/4 BSW is a BSW Whitworth thread: 19.05 mm major diameter, 10 TPI (2.54 mm pitch), 55° form. Tap drill 16.25 mm.

Minor diameters worked out from the basic profile: major Ø − 1.28065 × pitch.

Open 3/4 BSW 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.

Same diameter, other pitch

• 3/4-10 UNC10 TPI (2.54 mm pitch)
• 3/4-16 UNF16 TPI (1.588 mm pitch)

Close in size, won't mate

• 3/4-6 ACMEØ19.05 mm, 6 TPI
• M20Ø20 mm, 2.5 mm pitch
• M20×1.5Ø20 mm, 1.5 mm pitch
• M20×2Ø20 mm, 2 mm pitch
• Tr20×4Ø20 mm, 4 mm pitch

One size up or down

• 5/8 BSWØ15.88 mm (down)
• 7/8 BSWØ22.23 mm (up)

Got a bolt and no idea what it is? Measure the outside Ø and type it into Benchsmith → Find → Thread.