2-4 ACME thread: 50.8 mm × 4 TPI

Threads › 2-4 ACME

2-4 ACME is an Acme thread: 50.8 mm major diameter, 4 TPI (6.35 mm pitch), 29° form.

Standard	Acme
Major diameter	50.8 mm (2″)
Pitch	4 TPI (6.35 mm)
Thread angle	29°
Minor diameter, bolt	43.94 mm
Minor diameter, nut	43.94 mm
Tap drill	Not listed. Check your tap maker's chart.

Minor diameters worked out from the basic profile: major Ø − pitch − 0.508 mm.

Open 2-4 ACME in Benchsmith Add 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

2-4.5 UNCØ50.8 mm, 4.5 TPI
Tr50×8Ø50 mm, 8 mm pitch

One size up or down

1-3/4-4 ACMEØ44.45 mm (down)

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