Verified by Rachel Mayfield, Supply Chain Analyst - July 2026
An M14 hex nut (ISO 4032) measures 21.0 mm across flats, so it takes a 21.0 mm spanner or socket. Standard nut thickness is 12.8 mm maximum, the thread is M14 x 2.0 coarse, and the thin (jam) version per ISO 4035 is 7.0 mm thick. The full specification table, thin-nut data and DIN comparison are below.
M14 nut specification table
| Property | Value | Standard |
|---|
| Thread | M14 x 2.0 (coarse) | ISO 261 |
| Fine pitch option(s) | M14 x 1.5 | ISO 261 |
| Width across flats A/F (spanner size) | 21.0 mm | ISO 4032 |
| Legacy DIN 934 A/F (old stock) | 22.0 mm | DIN 934 |
| Width across corners (min) | 23.36 mm | ISO 4032 |
| Nut thickness (max), standard nut | 12.8 mm | ISO 4032 |
| Thin / jam nut thickness (max) | 7.0 mm | ISO 4035 |
M14 nut spanner size
The M14 hex nut takes a 21.0 mm spanner (width across flats per ISO 4032). Across corners the hexagon measures at least 23.36 mm, which is the clearance you need for a socket wall or a recessed nut pocket.
Watch for legacy stock: the older DIN 934 standard gave the M14 nut a 22.0 mm A/F instead of the current ISO 21.0 mm (the widths changed with ISO 272 in 1982). Old UK drawings and mixed fastener bins still contain DIN-size nuts, so if a 21.0 mm spanner slips on an M14 nut, try 22.0 mm before assuming the nut is damaged.
Standard, thin and nyloc M14 nuts
The standard M14 nut (ISO 4032, style 1) is 12.8 mm thick and is the default for general fastening. The thin or jam nut (ISO 4035) is 7.0 mm thick and is used for locking a standard nut in place or where axial space is tight - it is not a substitute for a full nut in a loaded joint. Thin nuts sold to the older DIN 439 standard keep the legacy 22.0 mm hexagon on this size, so check which standard the supplier quotes. Nyloc (nylon-insert) and other prevailing-torque nuts use the same hexagon as the standard nut but are taller; check the manufacturer's datasheet for exact heights.
M14 nut and bolt pairing
Match the property class of nut and bolt per ISO 898: a class 8 nut pairs with a class 8.8 bolt, class 10 with 10.9, class 12 with 12.9 (ISO 898-2). A nut of a higher class may always substitute a lower one, never the reverse - a lower-class nut on a high-class bolt shifts failure into thread stripping, which gives no visual warning before letting go. Proof-load values per class and nut style are tabulated in ISO 898-2; use the manufacturer's certified figures for critical joints. The mating bolt's full dimensions, torque values and tap drills are on the M14 bolt specifications card.
Related reference charts
Related standards
- ISO 4032 - Hexagon regular nuts, style 1, product grades A and B
- ISO 4035 - Hexagon thin nuts, chamfered
- ISO 898-2 - Mechanical properties of nuts with specified property classes
- ISO 261 - ISO general-purpose metric screw threads
- DIN 934 - Legacy hexagon nut standard (superseded, still in circulation)
Frequently Asked Questions
What spanner fits an M14 nut?
An M14 hex nut per ISO 4032 measures 21.0 mm across flats, so it takes a 21.0 mm spanner or socket. Legacy DIN 934 M14 nuts measure 22.0 mm across flats, so old stock may need a 22.0 mm spanner.
How thick is an M14 nut?
A standard M14 hex nut (ISO 4032, style 1) is 12.8 mm thick maximum. The thin or jam version (ISO 4035) is 7.0 mm thick.
What is the difference between ISO 4032 and DIN 934 M14 nuts?
For the M14 size the only practical difference is the hexagon: ISO 4032 uses 21.0 mm across flats while DIN 934 uses 22.0 mm. Thread, thickness and strength classes are interchangeable in practice, but the spanner size differs.
Which nut fits an M14 bolt?
A standard M14 bolt takes an M14 x 2.0 coarse-pitch nut (ISO 4032). Match the property class: class 8 nut for an 8.8 bolt, class 10 for 10.9, class 12 for 12.9. Fine-pitch bolts (M14 x 1.5) need matching fine-pitch nuts.
What class of nut goes with a class 8.8 M14 bolt?
Use a class 8 nut with a class 8.8 bolt (ISO 898-2). A higher-class nut may always substitute a lower one, never the reverse - a weaker nut on a strong bolt risks thread stripping below the bolt's rated load.