dimensielijn

Dimensielijn, or dimension line, is a feature in technical drawings that indicates the size or distance of a part or feature. It is a thin line with arrowheads at both ends, placed between extension lines that project from the feature being measured. The actual measurement—the value and unit—is shown as dimension text near or above the line. Extension lines anchor the dimension to the relevant points without touching the dimension line.

Components and types. A dimension line is supported by extension lines that touch the measured feature at right angles. Dimension lines can be linear (horizontal or vertical), angular, radial (for arcs and circles, indicating radius), or diameter (for circles and holes). The dimension text may indicate the value, plus tolerances, and sometimes the prefix or symbol (for example, R for radius or Ø for diameter).

Placement and conventions. Dimension lines are usually drawn outside the object whenever possible and kept clear of other lines. Extension lines extend from the feature to the dimension line and should not cross other features. Dimension text is aligned with the dimension line, and overlapping or clutter is avoided. In dense drawings, multiple dimensions may be organized using baseline or chain conventions, with care taken to minimize ambiguity.

Standards and usage. Dimensioning conventions follow international and national standards, such as ISO and ASME Y14.5, which define how dimension lines, extension lines, and tolerances should be presented. Dimensioning is used in both manual drafting and computer-aided design to communicate precise measurements for manufacturing and inspection.