M14 is one of the standard coarse-thread sizes for hex bolts under ISO 4014 / ISO 4017. The sections below reproduce the dimensional row, list the matching tools and hole sizes, and summarize where this size is normally specified.
M14 Dimensional Row (ISO 4014 / ISO 4017)
| Size | Pitch coarse (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k nom (mm) | Nominal diameter d (mm) | Reference standard | Notes |
|---|---|---|---|---|---|---|---|
| M14 | 2.0 | 21.0 | 23.36 | 8.8 | 14.0 | ISO 4014/4017 | Partial / fully threaded |
Spanner & Drive for M14 Hex Bolts
M14 Hex Bolts have a width across flats of 21.0 mm — fit a 21.0 mm open-ended spanner or socket. In tight access a 6-point socket on the 21.0 mm flats gives the most engagement per degree of swing. Where the joint is torqued to a figure, a click wrench is the only way to reproduce it across a batch.
Hole Sizes for M14
| Coarse-thread pitch (ISO 724) | 2 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 15.5 mm |
| Tapping drill, coarse thread | 12 mm |
Tightening Torque for M14
| Class 8.8 (dry, ~µ 0.125) | ≈ 134 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 197 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 231 Nm |
Indicative dry-joint values. Lubrication can lower the required torque by 15–25%. Always confirm against the joint design, especially when going up a strength class.
Proof Load & Strength for M14
| Tensile stress area As (ISO 724) | 115 mm² |
|---|---|
| Proof load, class 8.8 | 67 kN |
| Proof load, class 10.9 | 96 kN |
| Proof load, class 12.9 | 112 kN |
| Min. ultimate tensile load, class 8.8 | 92 kN |
Proof load = tensile stress area × the proof stress Sp of the class, per ISO 898-1 — Sp is a lower figure than the yield stress Rp0.2 and the two are not interchangeable. The stress area is computed from this size's own diameter and pitch, so a fine-pitch designation gives the fine-pitch figure. Design the joint so the working preload stays below the proof load of the class selected.
Installation Tips for M14 Hex Bolts
- Use a 6-point socket where access allows — 12-point sockets are more prone to rounding the corners on smaller sizes.
- Serrated flanges need to sit directly on the joint face. A washer between the two removes the bite and leaves an ordinary bolted joint that is believed to be a locking one.
Mating Parts for M14
For M14, pair with a M14 hex nut (ISO 4032 / DIN 934) and, where used, a M14 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
Custom manufacturing · Made to drawing
Need hex bolts in a size this table does not list?
This page covers M14 hex bolts. Head form and drive can be specified to the assembly rather than to a standard: a larger bearing face, a security drive, or a socket sized for the tool already on the bench. Made by cold heading or hot forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
