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2.1: Line styles and types

  • Page ID
    3230
  • Learning Task 2

    Describe lines, lettering, and dimensioning in drawings

    The purpose of engineering drawings is to convey objective facts, whereas artistic drawings convey emotion or artistic sensitivity in some way.

    Engineering drawings and sketches need to display simplicity and uniformity, and they must be executed with speed. Engineering drawing has evolved into a language that uses an extensive set of conventions to convey information very precisely, with very little ambiguity.

    Standardization is also very important, as it aids internationalization; that is, people from different countries who speak different languages can read the same engineering drawing and interpret it the same way. To that end, drawings should be as free of notes and abbreviations as possible so that the meaning is conveyed graphically.

    Line styles and types

    Standard lines have been developed so that every drawing or sketch conveys the same meaning to everyone. In order to convey that meaning, the lines used in technical drawings have both a definite pattern and a definite thickness. Some lines are complete and others are broken. Some lines are thick and others are thin. A visible line, for example, is used to show the edges (or “outline”) of an object and to make it stand out for easy reading. This line is made thick and dark. On the other hand, a centre line, which locates the precise centre of a hole or shaft, is drawn thin and made with long and short dashes. This makes it easily distinguishable from the visible line.

    When you draw, use a fairly sharp pencil of the correct grade and try to maintain an even, consistent pressure to make it easier for you to produce acceptable lines (Figure 1). Study the line thicknesses (or “line weights”) shown in Figure 2 and practise making them.

    pencilHardnessGrades.png
    1. Lead grade and usage
    2. sectionLines.png
      extDimLine.png
      leaderLine.png
      pipeBreaks_1.png

      Curled lines to abbreviate a longer span of pipe.

    3. Weights of lines
      objectLine.png
    4. Object lines
      hiddenLines.png
    5. Hidden lines
      centreLine.png
    6. Centre lines
      dimensionLines.png
    7. Dimension and extension lines
      leaderLines.png
    8. Leader lines
      phantomLines.png
    9. Phantom lines
      cuttingPlaneLines.png
    10. Cutting plane lines
      sectionLines_1.png
    11. Section lines combined with cutting plane lines
      breakLines.png
    12. Break line