M4 Plain Washer are manufactured to GB/T 858 with a coarse thread pitch of 0.7 mm. This page lists the controlling dimensions for the M4 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M4 Dimensional Row (GB/T 858)
| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Reference standard |
|---|---|---|---|---|
| M4 | 4.3 | 9.0 | 0.8 | ISO 7089 / GB/T 97.1 |
Spanner & Drive for M4 Plain Washer — GB/T 858 (Series 071)
Drive geometry for M4 Plain Washer — GB/T 858 (Series 071) is given by the row above; match the tool to the listed values.
Common Applications for M4 Plain Washer — GB/T 858 (Series 071)
M4 Plain Washer — GB/T 858 (Series 071) are commonly specified for small electronics hardware and precision assemblies.
Mating Parts for M4
A M4 flat washer pairs with a M4 bolt/screw and matching M4 nut.
When to Step Up or Down from M4
When the joint preload approaches the proof load of M4 class 8.8, step up to M5 class 8.8 (or move to M4 class 10.9). When the joint is over-specified, M3 often saves weight and cost without losing the safety margin.