M18 Hex Nut (GB/T 6170 / ISO 4032) are specified by thread size, length and head dimensions. The M18 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M18 Dimensional Row (GB/T 6170 / ISO 4032)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|---|
| M18 | 2.5 | 27.0 | 30.14 | 15.8 | ISO 4032 / GB/T 6170 |
Spanner & Drive for M18 Hex Nut — GB/T 6170 / ISO 4032 (Series 059)
M18 Hex Nut — GB/T 6170 / ISO 4032 (Series 059) have a width across flats of 27.0 mm — fit a 27.0 mm open-ended spanner or socket. Use a 6-point socket for tight clearances and to reduce rounding; for repeated assembly choose a torque wrench so the joint preload is repeatable.
Common Applications for M18 Hex Nut — GB/T 6170 / ISO 4032 (Series 059)
M18 Hex Nut — GB/T 6170 / ISO 4032 (Series 059) are commonly specified for structural joints, flange connections and heavy equipment foundations.
Installation Tips for M18 Hex Nut — GB/T 6170 / ISO 4032 (Series 059)
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- On flanged or serrated variants, do NOT add a separate flat washer — the flange already spreads the load and the washer can defeat the locking serrations.
- At M18 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
Mating Parts for M18
Pair M18 with the matching M18 bolt or screw, plus a M18 flat washer where required to distribute load on softer materials.