For General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087), the M20 thread sits in the heavy-duty range of the catalog and is one of the most-asked general flat washer — gb/t 97.1 / iso 7089 (series 087) in this family. The dimensional and assembly data follow.
M20 Dimensional Row (GB/T 97.1 / ISO 7089)
| For bolt size | Inner diameter d1 (mm) | Outer diameter d2 (mm) | Thickness t (mm) | Reference standard |
|---|---|---|---|---|
| M20 | 21.0 | 37.0 | 3.0 | ISO 7089 / GB/T 97.1 |
Spanner & Drive for M20 General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087)
Drive geometry for M20 General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087) is given by the row above; match the tool to the listed values.
Common Applications for M20 General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087)
M20 General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087) are commonly specified for high-load load-spreading on structural joints.
Installation Tips for M20 General Flat Washer — GB/T 97.1 / ISO 7089 (Series 087)
- 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.
Mating Parts for M20
A M20 flat washer pairs with a M20 bolt/screw and matching M20 nut.
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.