This page covers M6 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).
M6 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) |
|---|---|---|---|---|---|---|
| M6 | 1.0 | 6 | 40 | 10.0 | 11.05 | 4.0 |
Spanner & Drive for M6 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M6 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) have a width across flats of 10.0 mm — fit a 10.0 mm open-ended spanner or socket. Prefer a 6-point socket over a 12-point: it loads the corners of the 10.0 mm hex far less, which matters on plated heads and on anything that will be re-used. Set preload with a torque wrench rather than by arm.
Hole Sizes for M6
| Coarse-thread pitch (ISO 724) | 1 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 6.6 mm |
| Tapping drill, coarse thread | 5 mm |
Tightening Torque for M6
| Class 8.8 (dry, ~µ 0.125) | ≈ 10 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 15 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 17 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 M6
| Tensile stress area As (ISO 724) | 20.1 mm² |
|---|---|
| Proof load, class 8.8 | 12 kN |
| Proof load, class 10.9 | 17 kN |
| Proof load, class 12.9 | 20 kN |
| Min. ultimate tensile load, class 8.8 | 16 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.
M6 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) Weight
A steel M6 hex bolt at the listed 40 mm length weighs approximately 12 g each — about 12 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 M6 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.
- A flanged head is its own washer. Adding a flat one under it lifts the serrations clear of the surface they are meant to bite, which is the whole locking mechanism gone.
Mating Parts for M6
For M6, pair with a M6 hex nut (ISO 4032 / DIN 934) and, where used, a M6 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 M6 hex bolt. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
