M8 Hex Nut are manufactured to GB/T 41 / ISO 4034. This page lists the controlling dimensions for the M8 size together with the drive and the installation notes for this type.
Values are taken from the governing standard rather than from a general machine-thread table, because this type is not selected on one.
M8 Dimensional Row (GB/T 41 / ISO 4034)
| 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 41 / ISO 4034 (Series 060)
M8 Hex Nut — GB/T 41 / ISO 4034 (Series 060) have a width across flats of 13.0 mm — fit a 13.0 mm open-ended spanner or socket. A 6-point socket grips all six flats of the 13.0 mm hex and is what to reach for once a fastener has been on and off a few times; a 12-point ring spanner starts rounding a worn head. For repeatable preload, torque rather than feel.
Tightening Torque for M8
| Class 8.8 (dry, ~µ 0.125) | ≈ 24 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 36 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 42 Nm |
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Proof Load & Strength for M8
Nuts are graded to ISO 898-2 by the proof load the nut itself will hold (classes 04, 05, 5, 6, 8, 10 and 12), not by the 8.8 / 10.9 / 12.9 scale used for bolts. A class-8 nut is the correct mate for a class-8.8 bolt, and the joint is designed on the bolt, so no bolt-tension figure is quoted here.
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.
Custom manufacturing · Made to drawing
Need hex nut in a size this table does not list?
This page covers M8 hex nut. Locking method is specifiable independently of the rest: nylon insert, all-metal deformed thread, serrated flange, or none. Made by cold heading or tapping.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
