M42 is one of the standard coarse-thread sizes for hex bolts, grade c under ISO 4016. The sections below reproduce the dimensional row, list the matching tools and hole sizes, and summarize where this size is normally specified.
M42 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 |
|---|---|---|---|---|---|---|
| M42 | 4.5 | 65.0 | 71.3 | 27.05 | Grade C | ISO 4016 / DIN 601 |
Spanner & Drive for M42 Hex Bolts, Grade C
M42 Hex Bolts, Grade C have a width across flats of 65.0 mm — fit a 65.0 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.
Common Applications for M42 Hex Bolts, Grade C
M42 Hex Bolts, Grade C are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Installation Tips for M42 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.
- At M42 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 M42
For M42, pair with a M42 hex nut (ISO 4032 / DIN 934) and, where used, a M42 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
