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M22×2.5 — 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)
19.5 mm
Nearest inch drill: 49/64 (0.7656") · Clearance hole (normal fit): 24 mm ·
8.8 torque: 581 N·m dry
Thread dimensions
Major diameter
22 mm
Pitch
2.5 mm
TPI (equivalent)
10.16
Pitch diameter
20.376 mm
Minor diameter
19.294 mm
Tensile stress area
303.4 mm²
Tap drill sizes for M22×2.5
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% | 20.376 mm | 20.4 mm | 0.7969" (51/64 drill) |
| 65% | 19.889 mm | 19.9 mm | 0.7812" (25/32 drill) |
| 75% | 19.564 mm | 19.5 mm | 0.7656" (49/64 drill) |
| 85% | 19.24 mm | 19.2 mm | 0.7500" (3/4 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 M22×2.5
| Fit | Hole | Use |
|---|---|---|
| Close | 23 mm | Located joints, dowel-like alignment |
| Normal | 24 mm | General assembly — use this unless you have a reason not to |
| Loose | 26 mm | Weldments, sheet stacks, tolerance build-up |
M22×2.5 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 | 225 N·m | 169 N·m | 166 lb-ft | 51.2 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 581 N·m | 436 N·m | 428 lb-ft | 132 kN |
| 10.9 Alloy steel, Q&T — high strength | 831 N·m | 623 N·m | 613 lb-ft | 188.9 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 971 N·m | 728 N·m | 716 lb-ft | 220.7 kN |
| A2-70 304 stainless, cold worked | 451 N·m | 338 N·m | 332 lb-ft | 102.4 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
34 mm or 32 mm (DIN)
Hex key (socket head)
17 mm