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M45×4.5 — 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)
40.5 mm
Nearest inch drill: 51/32 (1.5938") · Clearance hole (normal fit): 48 mm ·
8.8 torque: 5113 N·m dry
Thread dimensions
Major diameter
45 mm
Pitch
4.5 mm
TPI (equivalent)
5.64
Pitch diameter
42.077 mm
Minor diameter
40.129 mm
Tensile stress area
1306.01 mm²
Tap drill sizes for M45×4.5
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% | 42.077 mm | 42 mm | 1.6562" (53/32 drill) |
| 65% | 41.2 mm | 41 mm | 1.6094" (103/64 drill) |
| 75% | 40.616 mm | 40.5 mm | 1.5938" (51/32 drill) |
| 85% | 40.031 mm | 40 mm | 1.5781" (101/64 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 M45×4.5
| Fit | Hole | Use |
|---|---|---|
| Close | 46 mm | Located joints, dowel-like alignment |
| Normal | 48 mm | General assembly — use this unless you have a reason not to |
| Loose | 52 mm | Weldments, sheet stacks, tolerance build-up |
M45×4.5 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 | 1983 N·m | 1488 N·m | 1463 lb-ft | 220.4 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 5113 N·m | 3835 N·m | 3771 lb-ft | 568.1 kN |
| 10.9 Alloy steel, Q&T — high strength | 7317 N·m | 5488 N·m | 5397 lb-ft | 813 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 8551 N·m | 6413 N·m | 6307 lb-ft | 950.1 kN |
| A2-70 304 stainless, cold worked | 3967 N·m | 2975 N·m | 2926 lb-ft | 440.8 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
70 mm
Hex key (socket head)
32 mm