For Hex Bolt — GB/T 6173 / ISO 8675 (Series 057), the M5 thread sits in the small-to-medium range of the catalog and is one of the most-asked hex bolt — gb/t 6173 / iso 8675 (series 057) in this family. The dimensional and assembly data follow.
M5 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) |
|---|---|---|---|---|---|---|
| M5 | 0.8 | 5 | 30 | 8.0 | 8.79 | 3.5 |
Spanner & Drive for M5 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M5 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) have a width across flats of 8.0 mm — fit a 8.0 mm open-ended spanner or socket. Use a 6-point socket for tight clearances and to reduce rounding; for repeated assembly choose a torque wrench so the joint preload is repeatable.
Hole Sizes for M5
| Coarse-thread pitch (ISO 724) | 0.8 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 5.5 mm |
| Tapping drill, coarse thread | 4.2 mm |
Tightening Torque for M5
| Class 8.8 (dry, ~µ 0.125) | ≈ 5.8 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 8.1 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 9.7 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.
Common Applications for M5 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M5 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) are commonly specified for precision instruments, small machinery and consumer-electronics enclosures.
Installation Tips for M5 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.
- On flanged or serrated variants, do NOT add a separate flat washer — the flange already spreads the load and the washer can defeat the locking serrations.
- At M5 the joint is sensitive to over-torque — use a torque-limiting driver and check the head doesn't bury into a softer counterpart.
When to Step Up or Down from M5
When the joint preload approaches the proof load of M5 class 8.8, step up to M6 class 8.8 (or move to M5 class 10.9). When the joint is over-specified, M4 often saves weight and cost without losing the safety margin.