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M8×0.75 — 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)
7.25 mm
Nearest inch drill: 9/32 (0.2812") · Clearance hole (normal fit): 9 mm ·
8.8 torque: 29.1 N·m dry
Thread dimensions
Major diameter
8 mm
Pitch
0.75 mm
TPI (equivalent)
33.87
Pitch diameter
7.513 mm
Minor diameter
7.188 mm
Tensile stress area
41.81 mm²
Tap drill sizes for M8×0.75
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% | 7.513 mm | 7.5 mm | 0.2950" (M drill) |
| 65% | 7.367 mm | 7.4 mm | 0.2900" (L drill) |
| 75% | 7.269 mm | 7.25 mm | 0.2812" (9/32 drill) |
| 85% | 7.172 mm | 7.2 mm | 0.2812" (9/32 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 M8×0.75
| Fit | Hole | Use |
|---|---|---|
| Close | 8.4 mm | Located joints, dowel-like alignment |
| Normal | 9 mm | General assembly — use this unless you have a reason not to |
| Loose | 10 mm | Weldments, sheet stacks, tolerance build-up |
M8×0.75 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 | 11.3 N·m | 8.47 N·m | 8.33 lb-ft | 7.1 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 29.1 N·m | 21.8 N·m | 21.5 lb-ft | 18.2 kN |
| 10.9 Alloy steel, Q&T — high strength | 41.6 N·m | 31.2 N·m | 30.7 lb-ft | 26 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 48.7 N·m | 36.5 N·m | 35.9 lb-ft | 30.4 kN |
| A2-70 304 stainless, cold worked | 22.6 N·m | 16.9 N·m | 16.7 lb-ft | 14.1 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
13 mm
Hex key (socket head)
6 mm