Page:Sheet Metal Drafting.djvu/26

12 9. The Sheet Metal Cleat.—The work of this problem will consist in laying out, to full size, the views and pattern for a galvanized sheet metal cleat. In making the layout for this cleat, the following points must be kept in mind:


 * 1) The proper relation of views in a drawing.
 * 2) How to dimension a drawing.
 * 3) Accuracy in the use of the scale rule.

This cleat is to be formed from a flat piece of No. 16 galvanized iron; all the bends to be made to an angle of 90°. Figure 17 represents the cleat as it would appear on a photograph.

Before starting the layout, it must first be determined how many faces the cleat has. By holding the cleat with the largest surface directly in front of the eyes, three of these faces can be seen. A drawing should be made of what is actually seen. This drawing would appear as shown in Fig. 18. This view is called the front elevation and from it the exact sizes of the three faces or surfaces shown can be determined.

If the cleat is turned so that the eyes see the thin edge of the metal, the view will be as shown in Fig. 19. This view is called the profile because it is the exact shape or outline to which the cleat must be formed in the shop.

In drawing the profile, it can be located directly under the front elevation by using extension lines such as shown. In addition to showing the exact outline of the cleat, the profile also shows the dimensions necessary for laying out the pattern. In order to transfer these dimensions to the line of stretchout on the pattern, the profile should be numbered as indicated.

The front elevation and profile furnish all the information required to lay out the pattern. Consequently, there is no need to draw other views.

The line of stretchout is always drawn at right angles to the side of the view from which the pattern is to be taken. Upon this line of stretchout, all of the distances (called the spacing of the profile) of the profile should be placed and numbered to correspond. This has been done in Fig. 20. Perpendicular lines are then drawn through these numbered points. These are called the