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M16×1.5 — 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)
14.5 mm
Nearest inch drill: 37/64 (0.5781") · Clearance hole (normal fit): 17.5 mm ·
8.8 torque: 233 N·m dry
Thread dimensions
Major diameter
16 mm
Pitch
1.5 mm
TPI (equivalent)
16.93
Pitch diameter
15.026 mm
Minor diameter
14.376 mm
Tensile stress area
167.25 mm²
Tap drill sizes for M16×1.5
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% | 15.026 mm | 15 mm | 0.5938" (19/32 drill) |
| 65% | 14.733 mm | 14.7 mm | 0.5781" (37/64 drill) |
| 75% | 14.539 mm | 14.5 mm | 0.5781" (37/64 drill) |
| 85% | 14.344 mm | 14.3 mm | 0.5625" (9/16 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 M16×1.5
| Fit | Hole | Use |
|---|---|---|
| Close | 17 mm | Located joints, dowel-like alignment |
| Normal | 17.5 mm | General assembly — use this unless you have a reason not to |
| Loose | 18.5 mm | Weldments, sheet stacks, tolerance build-up |
M16×1.5 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 | 90.3 N·m | 67.7 N·m | 66.6 lb-ft | 28.2 kN |
| 8.8 Medium-carbon, quenched & tempered — the default structural grade | 233 N·m | 175 N·m | 172 lb-ft | 72.8 kN |
| 10.9 Alloy steel, Q&T — high strength | 333 N·m | 250 N·m | 246 lb-ft | 104.1 kN |
| 12.9 Alloy steel, Q&T — highest common grade (socket head cap screws) | 389 N·m | 292 N·m | 287 lb-ft | 121.7 kN |
| A2-70 304 stainless, cold worked | 181 N·m | 135 N·m | 133 lb-ft | 56.4 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
24 mm
Hex key (socket head)
14 mm