M14 Bolt Specifications

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Reviewed by MLC Editorial Team | 16 August 2026

Verified by Rachel Mayfield, Supply Chain Analyst - May 2026

Close-up image of three steel bolts standing upright against a contrasting yellow background. — 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

References

ISO 261:1998 - ISO metric screw threads
ISO 898-1:2013 - Mechanical properties of fasteners
VDI 2230:2015 - Calculation of bolted joints

M14 bolts and tools on Amazon

Shop the exact parts and tools referenced above on Amazon UK. Prices, stock, and delivery times update live; MLC earns a small commission on qualifying purchases at no cost to you.

Buy M14 hex bolts (DIN 933) on Amazon →
Buy M14 socket cap screws on Amazon →
Buy M14 hex key (12mm) on Amazon →
Buy M14 spanner (21mm ISO / 22mm DIN) on Amazon →
Buy Torque wrench for M14 (150Nm) on Amazon →

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Frequently Asked Questions

What is the thread pitch of an M14 bolt?

A standard M14 bolt has a coarse thread pitch of 2.0 mm per ISO 261. The fine pitch version is M14 x 1.5. If a drawing says M14 with no pitch specified, it means M14 x 2.0 coarse.

What is the tap drill size for M14?

For M14 x 2.0 coarse pitch with 75% thread engagement, drill 12.0 mm. For fine pitch, drill 12.5 mm. These values give a good balance of thread strength and tapping ease.

What torque is an M14 bolt rated for?

For a dry M14 property class 8.8 bolt, the standard torque is 135 Nm. Class 10.9 takes 190 Nm, class 12.9 takes 225 Nm. Values are per VDI 2230 at 90% proof load with nut factor K=0.20. Reduce by 20-25% if threads are lubricated.

What spanner size fits an M14 bolt?

An M14 hex head bolt (ISO 4014) has a 21.0 mm across-flats (A/F) dimension, so you need a 21.0 mm spanner or socket. An M14 socket head cap screw uses a 12.0 mm hex key (Allen key).

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