Page:Sheet Metal Drafting.djvu/16

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SHEET METAL DRAFTING

2. Orthographic Projection.—Before attempting to make any drawings, one must first get a clear idea of the way in which objects are represented in mechanical or orthographic drawings. If a person is going to make a photograph of an object, he nearly always makes a view taken from one corner so as to show as many sides as possible in order to give a complete idea of the object in one picture. For example, Fig. 1 shows how an anvil would be represented in a single view or picture so as to give a complete idea of its shape. Such a drawing of most objects would be very

Fig. 2.—Mechanical Drawing of Anvil.

complicated or difficult to make, and even then in many cases it would not give the complete idea. Instead of making a pictorial drawing, the draftsman makes two or more views as if he were looking straight at the different sides of the object as in Fig. 2.

At A is shown what would be called a "front elevation," meaning a view of one side taken from the front with the anvil set up in its natural position. At D is shown the "plan" or top view. This shows what would be seen by looking down on the anvil from above along the direction of the arrow Y. At B and C are shown the views of the ends as seen by looking along the arrows, W and X. These views are called the "right end elevation" and