The M39 size of Hex Bolts is dimensioned by ISO 4014 / ISO 4017. The tables below give the dimensional row from the standard, the drill and spanner sizes that go with it, and the assembly torque per property class. The technical drawing on this page redraws to the exact values selected.
M39 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 |
|---|---|---|---|---|---|---|---|
| M39 | 4.0 | 60.0 | 66.44 | 25.0 | 39.0 | ISO 4014/4017 | Partial / fully threaded |
Spanner & Drive for M39 Hex Bolts
M39 Hex Bolts have a width across flats of 60.0 mm — fit a 60.0 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 M39 Hex Bolts
M39 Hex Bolts are commonly specified for structural steelwork, heavy machinery foundations and large flange joints.
Installation Tips for M39 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.
- At M39 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 M39
For M39, pair with a M39 hex nut (ISO 4032 / DIN 934) and, where used, a M39 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
