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M12×1.25 — Full Fastener Spec
ISO 68-1 / ISO 261 · Fine series · Tap drill, clearance hole, torque, strength and tool sizes — every number on one page.
Tap drill (75% thread)
10.8 mm
Nearest inch drill: 27/64 (0.4219") · Clearance hole (normal fit): 13.5 mm ·
8.8 torque: 96.1 N·m dry
Thread dimensions
Major diameter
12 mm
Pitch
1.25 mm
TPI (equivalent)
20.32
Pitch diameter
11.188 mm
Minor diameter
10.647 mm
Tensile stress area
92.07 mm²
Tap drill sizes for M12×1.25
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% | 11.188 mm | 11.2 mm | 0.4375" (7/16 drill) |
| 65% | 10.945 mm | 10.9 mm | 0.4219" (27/64 drill) |
| 75% | 10.782 mm | 10.8 mm | 0.4219" (27/64 drill) |
| 85% | 10.62 mm | 10.6 mm | 0.4130" (Z 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 M12×1.25
| Fit | Hole | Use |
|---|---|---|
| Close | 13 mm | Located joints, dowel-like alignment |
| Normal | 13.5 mm | General assembly — use this unless you have a reason not to |
| Loose | 14.5 mm | Weldments, sheet stacks, tolerance build-up |
M12×1.25 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 | 37.3 N·m | 28 N·m | 27.5 lb-ft | 15.5 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 96.1 N·m | 72.1 N·m | 70.9 lb-ft | 40.1 kN |
| 10.9 Alloy steel, Q&T — high strength | 138 N·m | 103 N·m | 101 lb-ft | 57.3 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 161 N·m | 121 N·m | 119 lb-ft | 67 kN |
| A2-70 304 stainless, cold worked | 74.6 N·m | 55.9 N·m | 55 lb-ft | 31.1 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
18 mm or 19 mm (DIN)
Hex key (socket head)
10 mm