Dimensional and assembly data for M2.5 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.
M2.5 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 |
|---|---|---|---|---|---|---|---|
| M2.5 | 0.45 | 5.0 | 5.45 | 1.7 | 2.5 | ISO 4014/4017 | Fully threaded |
Spanner & Drive for M2.5 Hex Bolts
M2.5 Hex Bolts have a width across flats of 5.0 mm — fit a 5.0 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 M2.5 Hex Bolts
M2.5 Hex Bolts are commonly specified for precision instruments, small machinery and consumer-electronics enclosures.
Installation Tips for M2.5 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 M2.5 the joint is sensitive to over-torque — use a torque-limiting driver and check the head doesn't bury into a softer counterpart.
Mating Parts for M2.5
For M2.5, pair with a M2.5 hex nut (ISO 4032 / DIN 934) and, where used, a M2.5 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.
