M18×1.5 thread: 18 × 1.5 mm

Threads › M18×1.5

M18×1.5 is an ISO metric fine thread: 18 mm major diameter, 1.5 mm pitch, 60° form. Tap drill 16.5 mm. Clearance hole 19 mm (close) or 20 mm (normal).

Standard	ISO metric fine
Major diameter	18 mm
Pitch	1.5 mm
Thread angle	60°
Minor diameter, bolt	16.16 mm
Minor diameter, nut	16.38 mm
Tap drill	16.5 mm
Clearance hole	19 mm close, 20 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 M18×1.5 in Benchsmith Add to order list

What the call-out means

`M`	ISO metric
`18`	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

M182.5 mm pitch
M18×22 mm pitch

Close in size, won't mate

Tr18×4Ø18 mm, 4 mm pitch
3/8-18 NPTØ17.15 mm, 18 TPI

One size up or down

M16×1.5Ø16 mm (down)
M20×2Ø20 mm (up)

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