Home › M24×3
M24×3 — Full Fastener Spec
ISO 68-1 / ISO 261 · Coarse series · Tap drill, clearance hole, torque, strength and tool sizes — every number on one page.
Tap drill (75% thread)
21 mm
Nearest inch drill: 53/64 (0.8281") · Clearance hole (normal fit): 26 mm ·
8.8 torque: 736 N·m dry
Thread dimensions
Major diameter
24 mm
Pitch
3 mm
TPI (equivalent)
8.47
Pitch diameter
22.052 mm
Minor diameter
20.753 mm
Tensile stress area
352.5 mm²
Tap drill sizes for M24×3
Percent of thread is a trade-off: 75% is the shop default because the last 25% of engagement adds only a few percent of strength while roughly doubling tapping torque. Drop to 50–65% in tough or gummy material, or for blind holes where a snapped tap means scrapping the part.
| Thread engagement | Exact | Metric drill | Nearest inch drill |
|---|---|---|---|
| 50% | 22.051 mm | 22.1 mm | 0.8750" (7/8 drill) |
| 65% | 21.467 mm | 21.5 mm | 0.8438" (27/32 drill) |
| 75% | 21.077 mm | 21 mm | 0.8281" (53/64 drill) |
| 85% | 20.687 mm | 20.7 mm | 0.8125" (13/16 drill) |
Roll (form) taps need a larger hole than cut taps — add roughly
0.4× the pitch to the 75% cut-tap drill and confirm against your tap maker's chart.
Clearance hole for M24×3
| Fit | Hole | Use |
|---|---|---|
| Close | 25 mm | Located joints, dowel-like alignment |
| Normal | 26 mm | General assembly — use this unless you have a reason not to |
| Loose | 28 mm | Weldments, sheet stacks, tolerance build-up |
M24×3 torque specs
Calculated with the short-form equation T = K · D · F, using K = 0.2 (plain, dry, as-received steel) and a target clamp load of 75% of proof load — the standard preload target for a reusable joint.
| Grade | Dry | Lubricated | Dry (lb-ft) | Clamp load |
|---|---|---|---|---|
| 4.6 Low-carbon steel, general purpose | 286 N·m | 214 N·m | 211 lb-ft | 59.5 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 736 N·m | 552 N·m | 543 lb-ft | 153.3 kN |
| 10.9 Alloy steel, Q&T — high strength | 1053 N·m | 790 N·m | 777 lb-ft | 219.4 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 1231 N·m | 923 N·m | 908 lb-ft | 256.4 kN |
| A2-70 304 stainless, cold worked | 571 N·m | 428 N·m | 421 lb-ft | 119 kN |
The nut factor K dominates this result. Zinc-plated, waxed, anti-seize
and lubricated threads all shift K between roughly 0.10 and 0.25, which is a 2.5×
spread in torque for identical preload. If preload actually matters, torque-to-yield,
angle control or a load-indicating washer beats a torque wrench every time.
Tool sizes
Hex head wrench
36 mm
Hex key (socket head)
19 mm