M8 Hex Nut are manufactured to GB/T 6170 / ISO 4032 with a coarse thread pitch of 1.25 mm. This page lists the controlling dimensions for the M8 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M8 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 |
|---|---|---|---|---|---|
| M8 | 1.25 | 13.0 | 14.38 | 6.8 | ISO 4032 / GB/T 6170 |
Spanner & Drive for M8 Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
M8 Hex Nut — GB/T 6170 / ISO 4032 (Series 066) have a width across flats of 13.0 mm — fit a 13.0 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 M8 Hex Nut — GB/T 6170 / ISO 4032 (Series 066)
M8 Hex Nut — GB/T 6170 / ISO 4032 (Series 066) are commonly specified for general-purpose joints in machinery, fixturing and equipment frames.
Mating Parts for M8
Pair M8 with the matching M8 bolt or screw, plus a M8 flat washer where required to distribute load on softer materials.
When to Step Up or Down from M8
When the joint preload approaches the proof load of M8 class 8.8, step up to M10 class 8.8 (or move to M8 class 10.9). When the joint is over-specified, M6 often saves weight and cost without losing the safety margin.