Hidden Lines in Orthographic Drawings

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Hidden Lines in Orthographic Drawings

• Technical Drawing
• Stuarts Draft High School

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HIDDEN LINES

• It is necessary to describe every part of an
  object. Therefore, everything must be represented
  in each view, whether or not it can be seen.
  Interior (inside) features and exterior (outside)
  features are both projected in the same way.
  Features that cannot be seen in a view are drawn
  with hidden lines, which are made up of short
  dashes. (See Fig. to right)

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HIDDEN LINES

• Notice that the first dash of a hidden line
  touches the line where it starts as in Fig. A.

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HIDDEN LINES

• If a hidden line is a continuation of a visible
  line, space is left between the visible line and
  the first dash of the hidden line, as at B.

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HIDDEN LINES

• If the hidden lines show corners, the dashes
  touch at the corners, as at C.

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HIDDEN LINES

• Dashes for hidden arcs (Fig. A) start and end at
  the tangent points.

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HIDDEN LINES

• When a hidden arc is tangent to a visible line, a
  space is left, as in Fig. B.

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HIDDEN LINES

• When a hidden line and a visible line project at
  the same place, show the visible line (See Fig.
  C)

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HIDDEN LINES

• When a centerline and a hidden line project at
  the same place (Fig. A), draw the hidden line.

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HIDDEN LINES

• When a hidden line crosses a visible line (Fig.
  B), do not cross the visible line with a dash.

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HIDDEN LINES

• When hidden lines cross (Fig. C), the nearest
  hidden line has the "right of way." Draw the
  nearest hidden line through a space of the
  farther hidden line.