å3

Ø3 is a conventional notation used in technical drawings to indicate a diameter of three units. The symbol Ø, known as the diameter symbol, accompanies a number to specify the size of a circular feature such as holes, bores, shafts, pipes, or cylindrical components. In practice, the units are implied by the drawing’s measurement system: in metric contexts, Ø3 usually means 3 millimeters in diameter, while in imperial contexts it could denote 3 inches.

The callout Ø3 does not by itself convey tolerances. Tolerances, surface finish, depth, or other constraints are provided separately in the drawing notes or in a geometric dimensioning and tolerancing (GD&T) frame. For example, a hole might be specified as Ø3 ±0.05, possibly with a depth or counterbore indicated elsewhere. When no unit or tolerance is stated, readers must rely on the drawing’s established standards or accompanying documentation.

Beyond holes, Ø3 can describe any cylindrical feature’s nominal diameter, including pins, bushings, tubes, or fittings. The diameter notation is widely used across engineering, manufacturing, carpentry, and mechanical design to avoid ambiguity with other measurements and to distinguish diameter from radius or other dimensions.

Etymology and usage: the symbol Ø originated as a typographic convention used to denote diameter in European engineering practice and has been standardized in many drawing conventions. It helps distinguish a full circular dimension from other measurements that may use similar symbols.