Dimensional and assembly data for M20 Thin Hex Castle Nut to GB/T 6181 / ISO 4035. Includes head size and width across flats, clearance-hole and tapping-drill diameters, tightening torque per property class, and the sizes to step up or down to when the joint requires it.
M20 Dimensional Row (GB/T 6181 / ISO 4035)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e (mm) | Total height m (mm) | Slot width (mm) | Reference standard |
|---|---|---|---|---|---|---|
| M20 | 2.5 | 30.0 | 33.53 | 24.0 | 5.5 | ISO 7036 / GB/T 6180 |
Spanner & Drive for M20 Thin Hex Castle Nut — GB/T 6181 / ISO 4035 (Series 053)
Drive geometry for M20 Thin Hex Castle Nut — GB/T 6181 / ISO 4035 (Series 053) is given by the row above; match the tool to the listed values.
Common Applications for M20 Thin Hex Castle Nut — GB/T 6181 / ISO 4035 (Series 053)
M20 Thin Hex Castle Nut — GB/T 6181 / ISO 4035 (Series 053) are commonly specified for structural joints, flange connections and heavy equipment foundations.
Installation Tips for M20 Thin Hex Castle Nut — GB/T 6181 / ISO 4035 (Series 053)
- At M20 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
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.