For Hex Bolts, Grade C, the M16 thread sits in the medium range of the catalog and is one of the most-asked hex bolts, grade c in this family. The dimensional and assembly data follow.
M16 Dimensional Row (ISO 4016)
| Size | Pitch (mm) | Width across flats s (mm) | Width across corners e min (mm) | Head height k (mm) | Product grade | Reference standard |
|---|---|---|---|---|---|---|
| M16 | 2.0 | 24.0 | 26.75 | 10.18 | Grade C | ISO 4016 / DIN 601 |
Spanner & Drive for M16 Hex Bolts, Grade C
M16 Hex Bolts, Grade C have a width across flats of 24.0 mm — fit a 24.0 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 M16
| Coarse-thread pitch (ISO 724) | 2 mm |
|---|---|
| Through-hole / clearance (ISO 273 medium) | 17.5 mm |
| Tapping drill, coarse thread | 14 mm |
Tightening Torque for M16
| Class 8.8 (dry, ~µ 0.125) | ≈ 210 Nm |
|---|---|
| Class 10.9 (dry, ~µ 0.125) | ≈ 295 Nm |
| Class 12.9 (dry, ~µ 0.125) | ≈ 355 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.
Common Applications for M16 Hex Bolts, Grade C
M16 Hex Bolts, Grade C are commonly specified for medium-duty structural connections, automotive sub-frames and equipment chassis.
Installation Tips for M16 Hex Bolts, Grade C
- 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.
When to Step Up or Down from M16
When the joint preload approaches the proof load of M16 class 8.8, step up to M20 class 8.8 (or move to M16 class 10.9). When the joint is over-specified, M12 often saves weight and cost without losing the safety margin.