DRAFTING TEMPLATES

Engineering Aid 3 - Beginning Structural engineering guide book
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on the graphical scale really registers 1 in. on the dial; if not, make the proper correction to the distance measured. Actually, a map measure is just another odometer. Odometers are used to measure actual distances, while the map measures are used to measure scaled distances. There are many ways of indicating the scale on a drawing. Among these are the fractional method, the equation method, and the graphic method. In the fractional method, the scale is indicated as a fraction or a ratio. A full-size scale is indicated as 1/1; enlarged scale, as 10/1, 4/1, 2/1, etc.; and reduced scale, as 1/2, 1/4, 1/10, etc. Notice that the drawing unit is always given as the numerator of the fraction and the object unit as the denominator. On maps, the reduced scale fraction may be very large (for example, 1/50,000), as compared with the typical scales on machine drawings. On maps, the scale is frequently expressed as a ratio, such as 1:50,000. In the equation method, a certain number of inches on the drawing is set equal to a certain length on the object. Symbols are used for feet (') and inches ("). On architectural drawings, a certain number of inches on the drawing is set to equal to 1 foot on the object. A full-size scale is entered as 12" = 1' – 0"; an enlarged scale, as 24" = 1’–0"; and a reduced scale, as 1/8" = 1' – 0". On civil engineering drawings, 1 in. on the drawing is set to equal to a certain measurement on the object: 1" = 5', 1" = 100', 1" = 1 mi. In the graphic method, an actual measuring scale is shown on the drawing. Typical graphic scales are shown in figure 2-29. Note that in each case, the primary scale lies to the right of the 0; a subdivided primary scale unit lies to the left of the 0. DRAFTING TEMPLATES DRAFTING TEMPLATES are timesaving devices that are used for drawing various shapes and standard symbols. They are especially useful when shapes and symbols must appear on the drawing a number of times. Templates are usually made of transparent green or clear plastic. They are available in a wide variety of shapes, including circles, ellipses, hexagons, triangles, rectangles, and arcs. Special templates are available for symbols used on architectural drawings, mechan- ical drawings, and maps. Templates for almost every purpose are available from the well-known drafting supply companies. Figure 2-30 shows only a few of the more common types of drafting templates. drafting templates draftsman kit. One set of commonly used is included in the EA’s 65.124A Figure 2-29.-Typical graphic scales. 2-22

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