For Hex Nuts, Grade C, the M8 thread sits in the small-to-medium range of the catalog and is one of the most-asked hex nuts, grade c in this family. The dimensional and assembly data follow.
M8 Dimensional Row (ISO 4034)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Nut height m (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M8 | 1.25 | 13.0 | 14.2 | 6.8 | Grade C | ISO 4034 / DIN 555 |
Spanner & Drive for M8 Hex Nuts, Grade C
M8 Hex Nuts, Grade C 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 Nuts, Grade C
M8 Hex Nuts, Grade C are commonly specified for general-purpose joints in machinery, fixturing and equipment frames.
Installation Tips for M8 Hex Nuts, Grade C
- 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.
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.