USE OF DRAFTING TEMPLATES

Engineering Aid 3 - Beginning Structural engineering guide book
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sharper the curve, the more points you need) and by drawing in shorts steps. Figure 3-10 shows how a smooth line is drawn through a series of plotted points. The french curve in view A matches points 1, 2, 3, and 4. Draw a line from 1 to 3 only (not to 4). At B, the curve matches points 3 to beyond 4. Draw a line from 3 to 4 only (not to 5). At C, it matches points 4, 5, and 6. Draw a line from 4 to just short of 6. At D, it matches a point short of 6 to beyond 7. Draw a line from 6 to 7. At E, it matches a point short of 7 to beyond 9. Draw a line from 7 to 9. At F, it matches a point short of 9 to beyond 11. Draw a line from 9 to 11. You will probably notice how the french curve is turned over and reversed to find portions that fit the points on the line with increasing or decreasing changes in curvature. When you are drawing a curved line that extends into a straight line, the curve should be drawn first, and the straight line joined to it. USE OF DRAFTING TEMPLATES Drafting templates should be used only when accuracy can be sacrificed for speed. Circles or arcs, for example, can be drawn more quickly with a template than with a compass. Templates must be used properly to be effective. To draw a circle with the circle template (fig. 3-11), lay out center lines on the drawing where Figure 3-11.-Use of the circle template. the circle is to be drawn. Then place the correct circle opening over the center line so that the quadrant lines on the template coincide with the center lines on the paper. Draw the circle, using a sharp, conical point on the pencil. Allowance must always be made for the width of the pencil line in placing the template opening in the right position on the drawing. To draw an arc, lay out tangent lines on the drawing. Then place the correct size circle of the template on the paper so that the template quadrant lines coincide with the tangent lines, and draw the arc. When using a template, you must hold it down firmly to keep it from slipping out of position. Figures or circles from the template must be drawn with the correct line weight on the first set- ting as it is difficult to reset the template in the exact position. USE OF THE DIVIDERS As we stated in chapter 2, dividers are used to transfer measurements, to step off a series of equal distances, and to divide lines into a number of equal parts. Dividers are manipulated with one hand. In setting dividers (fig. 3-12, view A), hold Figure 3-12.-Use of the dividers. 3-9

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