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M52×3 — 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)
49 mm
Nearest inch drill: 123/64 (1.9219") · Clearance hole (normal fit): 56 mm ·
8.8 torque: 8596 N·m dry
Thread dimensions
Major diameter
52 mm
Pitch
3 mm
TPI (equivalent)
8.47
Pitch diameter
50.051 mm
Minor diameter
48.752 mm
Tensile stress area
1900.04 mm²
Tap drill sizes for M52×3
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% | 50.051 mm | 50 mm | 1.9688" (63/32 drill) |
| 65% | 49.467 mm | 49.5 mm | 1.9531" (125/64 drill) |
| 75% | 49.077 mm | 49 mm | 1.9219" (123/64 drill) |
| 85% | 48.687 mm | 48.5 mm | 1.9062" (61/32 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 M52×3
| Fit | Hole | Use |
|---|---|---|
| Close | 54 mm | Located joints, dowel-like alignment |
| Normal | 56 mm | General assembly — use this unless you have a reason not to |
| Loose | 62 mm | Weldments, sheet stacks, tolerance build-up |
M52×3 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 | 3335 N·m | 2501 N·m | 2459 lb-ft | 320.6 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 8596 N·m | 6447 N·m | 6340 lb-ft | 826.5 kN |
| 10.9 Alloy steel, Q&T — high strength | 12301 N·m | 9226 N·m | 9073 lb-ft | 1182.8 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 14376 N·m | 10782 N·m | 10603 lb-ft | 1382.3 kN |
| A2-70 304 stainless, cold worked | 6669 N·m | 5002 N·m | 4919 lb-ft | 641.3 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
80 mm
Hex key (socket head)
36 mm