Dimensional and assembly data for M14 Hex Bolts to ISO 4014 / ISO 4017. Includes head size and width across flats, clearance-hole and tapping-drill diameters, tightening torque per property class, and the sizes to step up or down to when the joint requires it.
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. Use a 6-point socket for tight clearances and to reduce rounding; for repeated assembly choose a torque wrench so the joint preload is repeatable.
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) | ≈ 135 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 190 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 230 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 898-1) | 115 mm² |
|---|---|
| Proof load, class 8.8 | 67 kN |
| Proof load, class 10.9 | 95 kN |
| Proof load, class 12.9 | 112 kN |
| Min. ultimate tensile, class 8.8 | 92 kN |
Proof load = stress area × proof stress per ISO 898-1. Design joints so the working preload stays below the proof load of the selected class.
Common Applications for M14 Hex Bolts
M14 Hex Bolts are commonly specified for medium-duty structural connections, automotive sub-frames and equipment chassis.
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.
- On flanged or serrated variants, do NOT add a separate flat washer — the flange already spreads the load and the washer can defeat the locking serrations.
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.