M24 is one of the standard coarse-thread sizes for hex bolt under GB/T 5783 / ISO 4017. The sections below reproduce the dimensional row, list the matching tools and hole sizes, and summarize where this size is normally specified.
M24 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) |
|---|---|---|---|---|---|---|
| M24 | 3.0 | 24 | 150 | 36.0 | 39.98 | 15.0 |
Spanner & Drive for M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010)
M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) have a width across flats of 36.0 mm — fit a 36.0 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 M24
| Coarse-thread pitch (ISO 724) | 3 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 26 mm |
| Tapping drill, coarse thread | 21 mm |
Tightening Torque for M24
| Class 8.8 (dry, ~µ 0.125) | ≈ 710 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 1000 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 1200 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 M24
| Tensile stress area As (ISO 898-1) | 353 mm² |
|---|---|
| Proof load, class 8.8 | 212 kN |
| Proof load, class 10.9 | 293 kN |
| Proof load, class 12.9 | 342 kN |
| Min. ultimate tensile, class 8.8 | 282 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.
M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) Weight
A steel M24 hex bolt at the listed 150 mm length weighs approximately 665 g each — about 665 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 M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010)
M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010) are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Installation Tips for M24 Hex Bolt — GB/T 5783 / ISO 4017 (Series 010)
- 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 M24 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
Mating Parts for M24
For M24, pair with a M24 hex nut (ISO 4032 / DIN 934) and, where used, a M24 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.