M20 Eye Bolts are manufactured to DIN 580 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 (DIN 580)
| Thread size | Pitch (mm) | Ring inside diameter d (mm) | Ring outside diameter (mm) | Thread length (mm) | Max load vertical (kg) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M20 | 2.5 | 56 | 99 | 40 | 1200 | DIN 580 / WLL | Drop-forged lifting eye bolt, vertical pull |
Spanner & Drive for M20 Eye Bolts
Drive geometry for M20 Eye Bolts 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 Eye Bolts Weight
A steel M20 eye bolts at the listed 40 mm length weighs approximately 773 g each — about 773 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 Eye Bolts
M20 Eye Bolts are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Mating Parts for M20
For M20, pair with a M20 hex nut (ISO 4032 / DIN 934) and, where used, a M20 flat washer (ISO 7089 / DIN 125A) under the head and under the 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.