Dimensional and assembly data for M20 Swing Bolt to GB/T 77 / ISO 4026. 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 77 / ISO 4026)
| Thread size | Pitch (mm) | Ring outer dia D (mm) | Ring wire dia (mm) | Total length L (mm) | SWL (kg, axial) | Reference standard |
|---|---|---|---|---|---|---|
| M20 | 2.5 | 40 | 16 | 72 | 1200 | DIN 580 / GB/T 825 |
Spanner & Drive for M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020)
Drive geometry for M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020) is given by the row above; match the tool to the listed values.
Hole Sizes for M20
| Coarse-thread pitch (ISO 724) | 2.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 22 mm |
| Tapping drill, coarse thread | 17.5 mm |
Tightening Torque for M20
| Class 8.8 (dry, ~µ 0.125) | ≈ 410 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 580 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 690 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 M20
| Tensile stress area As (ISO 898-1) | 245 mm² |
|---|---|
| Proof load, class 8.8 | 147 kN |
| Proof load, class 10.9 | 203 kN |
| Proof load, class 12.9 | 238 kN |
| Min. ultimate tensile, class 8.8 | 196 kN |
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020) Weight
A steel M20 swing bolt at the listed 72 mm length weighs approximately 178 g each — about 178 kg per 1,000 pieces. Stainless A2/A4 weighs roughly the same (density 7.9–8.0 g/cm³). Actual weight varies slightly with head form, thread and finish; use this figure for freight estimation only.
Common Applications for M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020)
M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020) are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Installation Tips for M20 Swing Bolt — GB/T 77 / ISO 4026 (Series 020)
- 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.