On the bench specifying M4 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)? This page gives the controlling dimensions for the M4 size of Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) (to GB/T 6173 / ISO 8675).
M4 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) |
|---|---|---|---|---|---|---|
| M4 | 0.7 | 4 | 25 | 7.0 | 7.66 | 2.8 |
Spanner & Drive for M4 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M4 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) have a width across flats of 7.0 mm — fit a 7.0 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 M4
| Coarse-thread pitch (ISO 724) | 0.7 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 4.5 mm |
| Tapping drill, coarse thread | 3.3 mm |
Tightening Torque for M4
| Class 8.8 (dry, ~µ 0.125) | ≈ 2.9 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 4.1 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 4.9 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 M4 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057)
M4 Hex Bolt — GB/T 6173 / ISO 8675 (Series 057) are commonly specified for precision instruments, small machinery and consumer-electronics enclosures.
Installation Tips for M4 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 M4 the joint is sensitive to over-torque — use a torque-limiting driver and check the head doesn't bury into a softer counterpart.
Mating Parts for M4
For M4, pair with a M4 hex nut (ISO 4032 / DIN 934) and, where used, a M4 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.