By | April 25, 2015

Lines of different types and thicknesses are used for graphical representation of objects. The types of lines and their applications are shown in below table. Typical applications of different types of lines are shown below.

Types of lines and their applications

Applications of lines

Applications of lines2

Thickness of Lines

Two thicknesses of lines are used in draughting practice. The ratio of the thick to thin line should not be less than 2:1. The thickness of lines should be chosen according to the size and type of the drawing from the following range:

0.18, 0.25, 0.35, 0.5, 0.7, 1, 1.4 and 2

It is recommended that the space between two parallel lines, including hatching, should never be less than 0.7 mm.

Order of Priority of Coinciding Lines

When two or more lines of different types coincide, the following order of priority should be observed:

  • Visible outlines and edges (Continuous thick lines, type A),
  • Hidden outlines and edges (Dashed line, type E or F),
  • Cutting planes (Chain thin, thick at ends and changes of cutting planes, type H),
  • Centre lines and lines of symmetry (Chain thin line, type G),
  • Centroidal lines (Chain thin double dashed line, type K),
  • Projection lines (Continuous thin line, type B).
Full Section | Half Section | Auxiliary Section Views

The invisible line technique and aixs representation should be followed as per the recommendations given below.

Invisible linesAxis lines

Termination of Leader Lines

A leader is a line referring to a feature (dimension, object, outline, etc.).

Leader lines should terminate,

  • with a dot, if they end within the outlines of an object,
  • with an arrow head, if they end on the outline of an object,
  • without dot or arrow head, if they end on a dimension line.

Termination of leader lines

It is common practice to omit hidden lines in an assembled view, when their use tends to confuse an already complex drawing or when the feature is sufficiently clear in another view; but it is not advisable for a beginner to do the same and he will have to show the hidden lines in his drawing practice.