M18 Slotted Hex Bolt (GB/T 5782 / ISO 4014) are specified by thread size, length and head dimensions. The M18 row from the standard is reproduced below, followed by the drill sizes, spanner size and torque values used when installing this size.
M18 Dimensional Row (GB/T 5782 / ISO 4014)
| Size | Pitch (mm) | Nominal diameter d (mm) | Length L (mm) | Width across flats s (mm) | Width across corners e (mm) | Head height k (mm) |
|---|---|---|---|---|---|---|
| M18 | 2.5 | 18 | 100 | 27.0 | 30.14 | 11.5 |
Spanner & Drive for M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005)
M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005) have a width across flats of 27.0 mm — fit a 27.0 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 M18
| Coarse-thread pitch (ISO 724) | 2.5 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 20 mm |
| Tapping drill, coarse thread | 15.5 mm |
Tightening Torque for M18
| Class 8.8 (dry, ~µ 0.125) | ≈ 290 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 405 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 485 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 M18
| Tensile stress area As (ISO 898-1) | 192 mm² |
|---|---|
| Proof load, class 8.8 | 115 kN |
| Proof load, class 10.9 | 159 kN |
| Proof load, class 12.9 | 186 kN |
| Min. ultimate tensile, class 8.8 | 154 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.
M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005) Weight
A steel M18 slotted hex bolt at the listed 100 mm length weighs approximately 257 g each — about 257 kg per 1,000 pieces. Stainless A2/A4 weighs roughly the same (density 7.9–8.0 g/cm³). Actual weight varies slightly with head form, thread and finish; use this figure for freight estimation only.
Common Applications for M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005)
M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005) are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Installation Tips for M18 Slotted Hex Bolt — GB/T 5782 / ISO 4014 (Series 005)
- 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.
- At M18 the stretch in the bolt becomes the controlling factor — for critical joints, use angle-controlled or stretch-controlled tightening instead of pure torque.
Mating Parts for M18
For M18, pair with a M18 hex nut (ISO 4032 / DIN 934) and, where used, a M18 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.