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M3×0.35 — 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)
2.65 mm
Nearest inch drill: #37 (0.1040") · Clearance hole (normal fit): 3.4 mm ·
8.8 torque: 1.46 N·m dry
Thread dimensions
Major diameter
3 mm
Pitch
0.35 mm
TPI (equivalent)
72.57
Pitch diameter
2.773 mm
Minor diameter
2.621 mm
Tensile stress area
5.61 mm²
Tap drill sizes for M3×0.35
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% | 2.773 mm | 2.8 mm | 0.1100" (#35 drill) |
| 65% | 2.704 mm | 2.7 mm | 0.1065" (#36 drill) |
| 75% | 2.659 mm | 2.65 mm | 0.1040" (#37 drill) |
| 85% | 2.614 mm | 2.6 mm | 0.1015" (#38 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 M3×0.35
| Fit | Hole | Use |
|---|---|---|
| Close | 3.2 mm | Located joints, dowel-like alignment |
| Normal | 3.4 mm | General assembly — use this unless you have a reason not to |
| Loose | 3.6 mm | Weldments, sheet stacks, tolerance build-up |
M3×0.35 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 | 0.568 N·m | 0.426 N·m | 0.419 lb-ft | 0.9 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 1.46 N·m | 1.1 N·m | 1.08 lb-ft | 2.4 kN |
| 10.9 Alloy steel, Q&T — high strength | 2.09 N·m | 1.57 N·m | 1.54 lb-ft | 3.5 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 2.45 N·m | 1.84 N·m | 1.8 lb-ft | 4.1 kN |
| A2-70 304 stainless, cold worked | 1.14 N·m | 0.851 N·m | 0.837 lb-ft | 1.9 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
5.5 mm
Hex key (socket head)
2.5 mm