A point is technically a line

To distinguish between lines with different meanings, different line types with different line thicknesses have been defined for technical drawing. To distinguish between lines with different meanings, different line types with different line thicknesses have been defined for technical drawing.

There are, for example, the narrow and thick solid lines, broken lines such as the dashed line or the dash-dotted line, etc. The rules for the different types of lines and their use are summarized in DIN ISO 128-20. It should also be noted that the term line includes straight lines and curves. A line always has a defined start and end point.

According to DIN ISO 128-20, there are the following line types in technical drawings:

1. Solid line, narrow

Application of the narrow solid line:

  • Dimension line
  • Witness line
  • Light edges
  • Note and reference lines
  • hatching
  • Short center lines
  • Thread root
  • Dimension line limit
  • Diagonal crosses that mark flat surfaces
  • Bending lines (for pipes and machined parts)
  • Framing (of test dimensions / shape and position tolerances and details)

2. Solid line, wide

Application of the wide solid line:

  • visible outlines
  • visible edge
  • Thread peaks
  • Limit of the usable thread length
  • Molding lines

3. Freehand line, narrow

Using the narrow freehand line:

  • Representation of boundaries of interrupted views and sections (drawn freehand)

4. Zigzag line, narrow

Application of the narrow zigzag line:

  • Representation of boundaries of interrupted views and sections (drawn with a drawing machine)

5th dashed line, narrow

Application of the narrow dashed line:

  • hidden edges
  • hidden outlines

6. Dashed line, wide

Application of the broad dashed line:

  • Marking of surface treatments

7. Dashed line, narrow

Application of the narrow dash-dot line:

  • Center line
  • Line of symmetry
  • Pitch circle (with holes)
  • Pitch circle (with toothing)

8. Dash line, wide

Using the broad dash-dotted line:

  • Cutting planes
  • Identification of dividing lines in sections
  • Marking of limited areas e.g. treatment

9. Dashed two-dot line:

Application of the two-dot chain line:

  • Centroid lines
  • Outlines of adjacent components
  • End positions of moving components