An extension line is a fundamental element used in technical drawings to define the precise extent of a dimension.
In technical drafting and engineering, an extension line is defined as a thin, solid line that extends from a feature on a drawing, such as an edge or a hole, to indicate the boundaries being measured by a corresponding dimension line. These lines are typically drawn perpendicular to the dimension line they serve.
Key characteristics and requirements for extension lines include:
- Appearance: They are depicted as thin, solid lines.
- Orientation: They run perpendicular to the dimension line.
- Purpose: They indicate which feature is associated with the dimension, clearly showing the start and end points of the measurement.
- Placement Detail: There should be a visible gap of approximately 1 mm between the feature's corners or edges and the starting point of the extension line. This gap helps distinguish the extension line from the object's lines and enhances clarity.
- Extension Beyond Dimension Line: Extension lines typically extend slightly beyond the dimension line to which they connect.
Understanding extension lines is crucial for interpreting technical drawings accurately, as they bridge the gap between the physical object represented and the dimensional information provided.
Consider the following visual representation principles often associated with extension lines:
- Extension lines should not cross dimension lines or other extension lines unnecessarily.
- When multiple dimensions are placed, extension lines can be shared if originating from the same feature edge.
By following these conventions, technical drawings become standardized and easy to read across different disciplines and organizations.
