Break lines

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BREAK LINES

The size of the graphic representation of an object is often reduced (usually for the purpose of economizing on paper space) by the use of a device called a break. Suppose, for example, you want to make a drawing of a rectangle 1 ft wide by 100 ft long to the scale of 1/12, or 1 in. = 1 ft. If you drew in the full length of the rectangle, you would need a sheet of paper 100 in. long. By using a break, you can reduce the length of the figure to a feasible length, as shown in figure 3-34.

Figure 3-34.-Use of proper line conventions for (A) short break, and (B) long break.

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 3-35.-Use of special breaks.

Figure 3-36.-Use of phantom lines.