M4 Hex Bolt (GB/T 5783 / ISO 4017) are specified by thread size, length and head dimensions. The M4 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M4 Dimensional Row (GB/T 5783 / ISO 4017)
| 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 5783 / ISO 4017 (Series 010)
M4 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) 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.
Proof Load & Strength for M4
| Tensile stress area As (ISO 898-1) | 8.78 mm² |
|---|---|
| Proof load, class 8.8 | 5.1 kN |
| Proof load, class 10.9 | 7.3 kN |
| Proof load, class 12.9 | 8.5 kN |
| Min. ultimate tensile, class 8.8 | 7 kN |
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
M4 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) Weight
A steel M4 hex bolt at the listed 25 mm length weighs approximately 3.4 g each — about 3.4 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.
Common Applications for M4 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010)
M4 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) are commonly specified for precision instruments, small machinery and consumer-electronics enclosures.
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.
When to Step Up or Down from M4
When the joint preload approaches the proof load of M4 class 8.8, step up to M5 class 8.8 (or move to M4 class 10.9). When the joint is over-specified, M3 often saves weight and cost without losing the safety margin.