This page covers M12 Hex Bolt to GB/T 6173 / ISO 8675: the full dimensional row, hole and tool sizes, proof-load data and typical applications. All values are taken from the governing standards (GB/T 6173 / ISO 8675 together with ISO 273, ISO 724 and ISO 898-1 where applicable).
M12 Dimensional Row (GB/T 6173 / ISO 8675)
| Size | Pitch (mm) | Nominal diameter d (mm) | Length L (mm) | Width across flats s (mm) | Width across corners e (mm) | Head height k (mm) |
|---|---|---|---|---|---|---|
| M12 | 1.75 | 12 | 80 | 18.0 | 20.03 | 7.5 |
Spanner & Drive for M12 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M12 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) have a width across flats of 18.0 mm — fit a 18.0 mm open-ended spanner or socket. In tight access a 6-point socket on the 18.0 mm flats gives the most engagement per degree of swing. Where the joint is torqued to a figure, a click wrench is the only way to reproduce it across a batch.
Hole Sizes for M12
| Coarse-thread pitch (ISO 724) | 1.75 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 13.5 mm |
| Tapping drill, coarse thread | 10.25 mm |
Tightening Torque for M12
| Class 8.8 (dry, ~µ 0.125) | ≈ 84 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 124 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 145 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 M12
| Tensile stress area As (ISO 724) | 84.3 mm² |
|---|---|
| Proof load, class 8.8 | 49 kN |
| Proof load, class 10.9 | 70 kN |
| Proof load, class 12.9 | 82 kN |
| Min. ultimate tensile load, class 8.8 | 67 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.
M12 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) Weight
A steel M12 hex bolt at the listed 80 mm length weighs approximately 88 g each — about 88 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 M12 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- Serrated flanges need to sit directly on the joint face. A washer between the two removes the bite and leaves an ordinary bolted joint that is believed to be a locking one.
Mating Parts for M12
For M12, pair with a M12 hex nut (ISO 4032 / DIN 934) and, where used, a M12 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Custom manufacturing · Made to drawing
Need hex bolt in a size this table does not list?
This page covers M12 hex bolt. Material and finish are usually what drives a special — a grade the standard part is not stocked in, or a coating chosen against a salt-spray figure instead of a default. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
