SHEET METAL SIZES

Metal thicknesses up to 0.25 inch (6mm) are usually designated by a series of gauge numbers. Figure 8-5 shows how to read them. Metal 0.25 inch and over is given in inch and millimeter sizes. In calling for the material size of sheet metal developments, it is customary to give the gauge number, type of gauge, and its inch or millimeter equivalent in brackets followed by the developed width and length (fig. 8-5).

TYPES OF DEVELOPMENT

A surface is said to be developable if a thin sheet of flexible material, such as paper, can be wrapped smoothly about its surface. Therefore, objects that have plane, flat, or single-curved surfaces are developable. But a surface that is double-curved or warped is not considered developable, and approximate methods must be used to develop it.

Figure 8-6.-Development of a rectangular box.

A spherical shape would be an example of an approximate development. The material would be stretched to compensate for small inaccuracies. For example, the coverings for a football or basketball are made in segments. Each segment is cut to an approximate developed shape, and the segments are then stretched and sewed together to give the desired shape.

The following pages cover developable and nondevelopable, or approximate, methods. For

Figure 8-7.-Development drawing with folding instructions.

examples, straight-line and radial-line development are developable forms. However, triangular development requires approximation.

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing