M20 Square Nut are manufactured to GB/T 39 / ISO 4034 with a coarse thread pitch of 2.5 mm. This page lists the controlling dimensions for the M20 size — head geometry, width across flats, matching spanner size — together with the clearance hole, tapping drill and tightening torque used at assembly.
M20 Dimensional Row (GB/T 39 / ISO 4034)
| Size | Pitch (mm) | Width across flats s (mm) | Nut height m (mm) | Reference standard |
|---|---|---|---|---|
| M20 | 2.5 | 30.0 | 12.0 | GB/T 39 / DIN 562 |
Spanner & Drive for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075)
Drive geometry for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075) is given by the row above; match the tool to the listed values.
Common Applications for M20 Square Nut — GB/T 39 / ISO 4034 (Series 075)
M20 Square Nut — GB/T 39 / ISO 4034 (Series 075) are commonly specified for structural joints, flange connections and heavy equipment foundations.
Mating Parts for M20
Pair M20 with the matching M20 bolt or screw, plus a M20 flat washer where required to distribute load on softer materials.
When to Step Up or Down from M20
When the joint preload approaches the proof load of M20 class 8.8, step up to M24 class 8.8 (or move to M20 class 10.9). When the joint is over-specified, M16 often saves weight and cost without losing the safety margin.