M3 is one of the standard coarse-thread sizes for flat washers under ISO 7089 / ISO 7093. The sections below reproduce the dimensional row, list the matching tools and hole sizes, and summarize where this size is normally specified.
M3 Dimensional Row (ISO 7089 / ISO 7093)
| For bolt size | Inner diameter d1 min (mm) | Outer diameter d2 max (mm) | Thickness h (mm) | Reference standard |
|---|---|---|---|---|
| M3 | 3.2 | 7.0 | 0.5 | ISO 7089 |
Spanner & Drive for M3 Flat Washers
Drive geometry for M3 Flat Washers is given by the row above; match the tool to the listed values.
Common Applications for M3 Flat Washers
M3 Flat Washers are commonly specified for small electronics hardware and precision assemblies.
Installation Tips for M3 Flat Washers
- At M3 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 M3
A M3 flat washer pairs with a M3 bolt/screw and matching M3 nut.

