M22 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 M22 metric bolt in one reference card. M22 Bolt Specifications M22 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	22.0 mm	ISO 261
Coarse pitch	2.5 mm	ISO 261
Fine pitch	2.0 / 1.5 mm	ISO 261
Tap drill (coarse, 75% engagement)	19.5 mm	ISO 2306
Tap drill (fine)	20.0 / 20.5 mm	ISO 2306
Clearance hole - close	23.0 mm	ISO 273
Clearance hole - medium	24.0 mm	ISO 273
Clearance hole - coarse	26.0 mm	ISO 273
Hex head A/F (spanner size)	34.0 mm	ISO 4014
Hex head height	14.0 mm	ISO 4014
Socket head cap screw head dia	33.0 mm	ISO 4762
Socket head hex key size	17.0 mm	ISO 4762
Tensile stress area	303 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	175.7 kN	ISO 898-1
Proof load 10.9	251.5 kN	ISO 898-1
Torque dry, class 8.8	550 Nm	VDI 2230
Torque dry, class 10.9	785 Nm	VDI 2230
Torque dry, class 12.9	920 Nm	VDI 2230

M22 thread pitch

Standard M22 bolts use a 2.5 mm coarse pitch. Fine pitch M22 x 2.0 is used where vibration resistance matters or in thin-wall components. Coarse pitch is the default - if a drawing says M22 with no pitch specified, it means M22 x 2.5 coarse.

M22 tap drill size

For M22 x 2.5 coarse pitch with 75% thread engagement, drill 19.5 mm. For fine pitch, drill 20.0 / 20.5 mm. Smaller drills give more engagement but increase tap breakage risk without meaningful strength gain.

M22 clearance hole

For a clearance hole where the bolt passes through, use 23.0 mm (close fit), 24.0 mm (medium), or 26.0 mm (coarse) per ISO 273.

M22 torque values

Dry M22 property class 8.8: torque to 550 Nm. Class 10.9: 785 Nm. Class 12.9: 920 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.

M22 spanner and hex key

An M22 hex head bolt (ISO 4014) has 34.0 mm across flats, so you need a 34.0 mm spanner or socket. M22 socket head cap screws (ISO 4762) have 33.0 mm head diameter and need a 17.0 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

M22 bolts and tools on Amazon

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Buy M22 hex bolts (DIN 933) on Amazon →
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Buy Torque wrench for M22 (550Nm) on Amazon →

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Frequently Asked Questions

What is the thread pitch of an M22 bolt?

A standard M22 bolt has a coarse thread pitch of 2.5 mm per ISO 261. The fine pitch version is M22 x 2.0 / 1.5. If a drawing says M22 with no pitch specified, it means M22 x 2.5 coarse.

What is the tap drill size for M22?

For M22 x 2.5 coarse pitch with 75% thread engagement, drill 19.5 mm. For fine pitch, drill 20.0 / 20.5 mm. These values give a good balance of thread strength and tapping ease.

What torque is an M22 bolt rated for?

For a dry M22 property class 8.8 bolt, the standard torque is 550 Nm. Class 10.9 takes 785 Nm, class 12.9 takes 920 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 M22 bolt?

An M22 hex head bolt (ISO 4014) has a 34.0 mm across-flats (A/F) dimension, so you need a 34.0 mm spanner or socket. An M22 socket head cap screw uses a 17.0 mm hex key (Allen key).

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