Copyright Goodheart-Willcox Co., Inc. Unit 2 Line Conventions and Lettering 23 for dimensional values within the dimension line. Leaders are thin, continuous lines characterized by an arrow on one end and a shoulder on the other. If the leader involves a descriptive note, the shoulder end of the line is vertically centered on the beginning or end of the note. As shown in the figure, the leader line can cross through extension lines, but the drafter tries to avoid crossing lines when possible. Miscellaneous Lines A few other lines should be discussed in this unit. As you progress through the textbook, you will encounter applications for these lines. These exam- ples will help to reinforce your ability to discuss the purpose and function of each line. Sometimes it is not practical to view a particular feature from the normal viewing arrangement. A dif- ferent viewing direction can be established with a viewing-plane line, Figure 2‑7. The viewing-plane line is equivalent in appearance to the cutting-plane line, but it simply “floats” outside of the object instead of being placed at a hypothetical cutting position. When used, the view is usually labeled at each elbow with a letter of the alphabet, such as A, and the resulting view is placed off to the side and identified, such as VIEW A-A. Two types of break lines are used in drawings to “break out” or “break off” a portion of a view. Long break lines are used to shorten objects that are constant in detail yet too long to fit on the drawing, such as a shovel handle or a long bar, Figure 2‑8. Long break lines are thin, straight lines with zigzags. The short break line is used in section view drawings if it is desirable for the cutting plane not to go all the way through an object, Figure 2‑8. It is also used if a partial view of a part is useful for arranging the views on the page. The short break line, if drawn by hand, should be freehand and thick. This line should not be an exaggerated zigzag like lightning or splintered wood, but should look more like rough granite. There is an exception when breaking long features such as round tubes or rods. In cases where round stock, such as shafts (solid) or pipe (tubular), needs to be broken, a conventional “S” break is used, Figure 2‑9. When the part to be broken is not round, a short break line or long break line can be used. Goodheart-Willcox Publisher Figure 2‑7. A viewing-plane line for a partial view is drawn the same as a cutting-plane line, although there are three standard options. This viewing-plane line indicates the direction for viewing VIEW A-A. VIEW A–A A A