M6 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.
M6 Dimensional Row (ISO 7089 / ISO 7093)
| For bolt size | Inner diameter d1 min (mm) | Outer diameter d2 max (mm) | Thickness h (mm) | Reference standard |
|---|---|---|---|---|
| M6 | 6.4 | 12.0 | 1.6 | ISO 7089 |
Spanner & Drive for M6 Flat Washers
Drive geometry for M6 Flat Washers is given by the row above; match the tool to the listed values.
Common Applications for M6 Flat Washers
M6 Flat Washers are commonly specified for general-purpose load-spreading and locking under machine bolts.
Mating Parts for M6
A M6 flat washer pairs with a M6 bolt/screw and matching M6 nut.
When to Step Up or Down from M6
When the joint preload approaches the proof load of M6 class 8.8, step up to M8 class 8.8 (or move to M6 class 10.9). When the joint is over-specified, M5 often saves weight and cost without losing the safety margin.

