M1 is one of the standard coarse-thread sizes for hex bolts under ISO 4014 / ISO 4017. The sections below reproduce the dimensional row, list the matching tools and hole sizes, and summarize where this size is normally specified.
M1 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 |
|---|---|---|---|---|---|---|---|
| M1 | 0.25 | 2.5 | 2.71 | 0.7 | 1.0 | ISO 4017 | Fully threaded |
Spanner & Drive for M1 Hex Bolts
M1 Hex Bolts have a width across flats of 2.5 mm — fit a 2.5 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 M1 Hex Bolts
M1 Hex Bolts are commonly specified for precision instruments, small machinery and consumer-electronics enclosures.
Installation Tips for M1 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 M1 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 M1
For M1, pair with a M1 hex nut (ISO 4032 / DIN 934) and, where used, a M1 flat washer (ISO 7089 / DIN 125A) under the head and under the nut.