This page covers M20 Hex Bolts, Fine Pitch to ISO 8765: the full dimensional row, hole and tool sizes, proof-load data and typical applications. All values are taken from the governing standards (ISO 8765 together with ISO 273, ISO 724 and ISO 898-1 where applicable).
M20 Dimensional Row (ISO 8765)
| Size | Fine pitch (mm) | Width across flats s (mm) | Head height k (mm) | Stress area As (mmu00b2) | Common length range (mm) | Property class | Reference standard |
|---|---|---|---|---|---|---|---|
| M20 | 1.5 | 30.0 | 12.5 | 272.0 | 50~200 | 8.8 / 10.9 | ISO 8765 |
Spanner & Drive for M20 Hex Bolts, Fine Pitch
Drive geometry for M20 Hex Bolts, Fine Pitch is given by the row above; match the tool to the listed values.
Hole Sizes for M20
| Coarse-thread pitch (ISO 724) | 1.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 22 mm |
| Tapping drill, coarse thread | 18.5 mm |
Tightening Torque for M20
| Class 8.8 (dry, ~µ 0.125) | ≈ 466 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 664 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 776 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 724) | 272 mm² |
|---|---|
| Proof load, class 8.8 | 163 kN |
| Proof load, class 10.9 | 225 kN |
| Proof load, class 12.9 | 263 kN |
| Min. ultimate tensile load, class 8.8 | 225 kN |
Proof load = tensile stress area × the proof stress Sp of the class, per ISO 898-1 — Sp is a lower figure than the yield stress Rp0.2 and the two are not interchangeable. The stress area is computed from this size's own diameter and pitch, so a fine-pitch designation gives the fine-pitch figure. Design the joint so the working preload stays below the proof load of the class selected.
M20 Hex Bolts, Fine Pitch Weight
A steel M20 hex bolts, fine pitch at the listed 50,200 mm length weighs approximately 123,877 g each — about 123,877 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.
Installation Tips for M20 Hex Bolts, Fine Pitch
- 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
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.
Custom manufacturing · Made to drawing
Need hex bolts, fine pitch in a size this table does not list?
This page covers M20 hex bolts, fine pitch. Thread size and pitch, length, property class, drive form, head geometry and head marking are all specifiable — the standard part is where it starts, not where it stops. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
