PHANTOM LINES

Engineering Aid 3 - Beginning Structural engineering guide book
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On the original object, the ratio of width to length is 1:100. You can see that on the drawing the ratio is much larger (roughly about 1:8). However, the break tells you that a considerable amount of the central part of the figure is presumed to be removed. The thick, wavy lines shown in view (A), figure 3-34, are used for a short break. A short break is indicated by solid, freehand lines, and is generally used for rectangular sections. For wooden rectangular sections, the breaks are made sharper (serrated appearance) rather than wavy. For long breaks, full, ruled lines with freehand zigzags are used, as shown in view (B), figure 3-34. For wider objects, a long break might have more than one pair of zigzag lines. For drawings made to a large scale, special conventions are used that apply to drawing breaks in such things as metal rods, tubes, or bars. The methods of drawing these breaks are shown in figure 3-35. PHANTOM LINES Phantom lines are used most frequently to indicate an alternate position of a moving part, as shown in the left-hand view of figure 3-36. The part in one position is drawn in full lines, while in the alternate position it is drawn in phantom lines. Phantom lines are also used to indicate a break when the nature of the object makes the use of the conventional type of break unfeasible. An example of this use of phantom lines is shown in the right-hand view of figure 3-36. Figure 3-36.-Use of phantom lines. SECTION LINES Sometimes the technical information conveyed by a drawing can best be shown by a view that represents the object as it would look if part of it were cut away. A view of this kind is called a section. The upper view of figure 3-37 shows a plan view of a pipe sleeve. The lower view is a section, Figure 3-35.-Use of special breaks. 3-24 Figure 3-37.-Drawing of a plan view and a full section.

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