1. Hidden Lines in Orthographic Drawings
Technical Drawing
Stuarts Draft High School

2. 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)

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

4. 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.

5. HIDDEN LINES
If the hidden lines show corners, the dashes touch at the corners, as at C.

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

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

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

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

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

11. 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.