M24 is one of the standard coarse-thread sizes for hex bolts, grade c under ISO 4016. 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 (ISO 4016)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M24 | 3.0 | 36.0 | 39.55 | 15.35 | Grade C | ISO 4016 / DIN 601 |
Spanner & Drive for M24 Hex Bolts, Grade C
M24 Hex Bolts, Grade C have a width across flats of 36.0 mm — fit a 36.0 mm open-ended spanner or socket. In tight access a 6-point socket on the 36.0 mm flats gives the most engagement per degree of swing. Where the joint is torqued to a figure, a click wrench is the only way to reproduce it across a batch.
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) | ≈ 726 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 1034 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 1210 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 724) | 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 load, class 8.8 | 293 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.
Installation Tips for M24 Hex Bolts, Grade C
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- Serrated flanges need to sit directly on the joint face. A washer between the two removes the bite and leaves an ordinary bolted joint that is believed to be a locking one.
- 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.
Custom manufacturing · Made to drawing
Need hex bolts, grade c in a size this table does not list?
This page covers M24 hex bolts, grade c. 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.
