M20×1.5 thread: 20 × 1.5 mm

Threads › M20×1.5

M20×1.5 is an ISO metric fine thread: 20 mm major diameter, 1.5 mm pitch, 60° form. Tap drill 18.5 mm. Clearance hole 21 mm (close) or 22 mm (normal).

Standard	ISO metric fine
Major diameter	20 mm
Pitch	1.5 mm
Thread angle	60°
Minor diameter, bolt	18.16 mm
Minor diameter, nut	18.38 mm
Tap drill	18.5 mm
Clearance hole	21 mm close, 22 mm normal
Usual class	6g bolt, 6H nut

Minor diameters worked out from the basic profile: major Ø − 1.22687 × pitch (bolt) and − 1.08253 × pitch (nut).

Open M20×1.5 in Benchsmith Add to order list

What the call-out means

`M`	ISO metric
`20`	Major diameter, mm
`× 1.5`	Pitch, mm. Given because it is a fine pitch
`-6g`	Bolt tolerance class (usual)
`-6H`	Nut tolerance class (usual)

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

M202.5 mm pitch
M20×22 mm pitch

Close in size, won't mate

Tr20×4Ø20 mm, 4 mm pitch
3/4-10 UNCØ19.05 mm, 10 TPI
3/4-16 UNFØ19.05 mm, 16 TPI
3/4 BSWØ19.05 mm, 10 TPI
3/4-6 ACMEØ19.05 mm, 6 TPI
G1/2Ø20.96 mm, 14 TPI

One size up or down

M18×1.5Ø18 mm (down)
M22×1.5Ø22 mm (up)

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