Verified by Rachel Mayfield, Supply Chain Analyst - May 2026
Photo by Győző Mórocz on Pexels
Every dimension, torque value, and thread specification for the M14 metric bolt in one reference card. M14 Bolt Specifications M14 is one of the most common metric fastener sizes in UK engineering, used across heavy structural and high-load joints.
| Property |
Value |
Standard |
| Nominal diameter |
14.0 mm |
ISO 261 |
| Coarse pitch |
2.0 mm |
ISO 261 |
| Fine pitch |
1.5 mm |
ISO 261 |
| Tap drill (coarse, 75% engagement) |
12.0 mm |
ISO 2306 |
| Tap drill (fine) |
12.5 mm |
ISO 2306 |
| Clearance hole - close |
15.0 mm |
ISO 273 |
| Clearance hole - medium |
15.5 mm |
ISO 273 |
| Clearance hole - coarse |
16.5 mm |
ISO 273 |
| Hex head A/F (spanner size) |
21.0 mm |
ISO 4014 |
| Hex head height |
8.8 mm |
ISO 4014 |
| Socket head cap screw head dia |
21.0 mm |
ISO 4762 |
| Socket head hex key size |
12.0 mm |
ISO 4762 |
| Tensile stress area |
115 mm^2 |
ISO 898-1 |
| Minimum tensile strength 8.8 |
800 MPa |
ISO 898-1 |
| Minimum tensile strength 10.9 |
1040 MPa |
ISO 898-1 |
| Proof load 8.8 |
66.7 kN |
ISO 898-1 |
| Proof load 10.9 |
95.5 kN |
ISO 898-1 |
| Torque dry, class 8.8 |
135 Nm |
VDI 2230 |
| Torque dry, class 10.9 |
190 Nm |
VDI 2230 |
| Torque dry, class 12.9 |
225 Nm |
VDI 2230 |
M14 thread pitch
Standard M14 bolts use a 2.0 mm coarse pitch. Fine pitch M14 x 1.5 is used where vibration resistance matters or in thin-wall components. Coarse pitch is the default - if a drawing says M14 with no pitch specified, it means M14 x 2.0 coarse.
M14 tap drill size
For M14 x 2.0 coarse pitch with 75% thread engagement, drill 12.0 mm. For fine pitch, drill 12.5 mm. Smaller drills give more engagement but increase tap breakage risk without meaningful strength gain.
M14 clearance hole
For a clearance hole where the bolt passes through, use 15.0 mm (close fit), 15.5 mm (medium), or 16.5 mm (coarse) per ISO 273.
M14 torque values
Dry M14 property class 8.8: torque to 135 Nm. Class 10.9: 190 Nm. Class 12.9: 225 Nm. These values target 90% proof load with K=0.20 dry thread friction. If threads are oiled or coated, reduce by 20-25%. For critical joints, always verify against the fastener manufacturer's datasheet.
M14 spanner and hex key
An M14 hex head bolt (ISO 4014) has 21.0 mm across flats, so you need a 21.0 mm spanner or socket. M14 socket head cap screws (ISO 4762) have 21.0 mm head diameter and need a 12.0 mm hex key (Allen key).
Related standards
- ISO 261 - ISO general-purpose metric screw threads
- ISO 273 - Fasteners: clearance holes for bolts and screws
- ISO 898-1 - Mechanical properties of carbon steel fasteners
- ISO 4014 - Hexagon head bolts, product grades A and B
- ISO 4762 - Hexagon socket head cap screws
- VDI 2230 - Systematic calculation of bolted joints
M14 bolts and tools on Amazon
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