#6-40 UNF thread: 3.51 mm × 40 TPI
Threads › #6-40 UNF
#6-40 UNF is a UNF thread: 3.51 mm major diameter, 40 TPI (0.635 mm pitch), 60° form.
| Standard | UNF |
|---|---|
| Major diameter | 3.505 mm (0.138″) |
| Pitch | 40 TPI (0.635 mm) |
| Thread angle | 60° |
| Minor diameter, bolt | 2.73 mm |
| Minor diameter, nut | 2.82 mm |
| Tap drill | Not listed. Check your tap maker's chart. |
| Usual class | 2A bolt, 2B nut |
Minor diameters worked out from the basic profile: major Ø − 1.22687 × pitch (bolt) and − 1.08253 × pitch (nut).
Open #6-40 UNF 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
- #6-32 UNC32 TPI (0.794 mm pitch)
Close in size, won't mate
- #5-40 UNCØ3.18 mm, 40 TPI
- 1/8 BSWØ3.18 mm, 40 TPI
- M4Ø4 mm, 0.7 mm pitch
- M3Ø3 mm, 0.5 mm pitch
- #8-32 UNCØ4.17 mm, 32 TPI
- #4-40 UNCØ2.84 mm, 40 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.