Imagine that you have line XY with A as a pointat which you need to fabricate a perpendicular to forma right angle. Select any convenient point that liessomewhere within the proposed 90-degree angle. Infigure 2-9 that point is C. Using C as the center of acircle with a radius equal to CA, scribe a semicirculararc, as shown in figure 2-9. Lay a straightedge alongpoints B and C and draw a line that will intersect theother end of the arc at D. Next, draw a line connectingthe points D and A and you have fabricated a90-degree angle. This procedure may be used to form90-degree comers in stretch-outs that are square orrectangular, like a drip pan or a box.Laying out a drip pan with a pair of dividers is nomore difficult than fabricating a perpendicular. Youwill need dividers, a scriber, a straightedge, and a sheetof template paper. You have the dimensions of the panto be fabricated: the length, the width, and the heightor depth. Draw a base line (fig. 2-10). Select a pointon this line for one comer of the drip pan layout. Erecta perpendicular through this point, forming a90-degree angle. Next, measure off on the base linethe required length of the pan. At this point, erectanother perpendicular. You now have three sides of thestretch-out. Using the required width of the pan for theother dimensions, draw the fourth side parallel to thebase line, connecting the two perpendiculars that youhave fabricated.Now, set the dividers for marking off the depth ofthe drip pan. You can use a steel scale to measure offthe correct radius on the dividers. Using each comerfor a point, swing a wide arc, like the one shown in thesecond step in figure 2-10. Extend the end and sidelines as shown in the last step in figure 2-10 andcomplete the stretch-out by connecting the arcs with ascriber and straightedge.Bisecting an arc is another geometric constructionthat you should be familiar with. Angle ABC (fig.2-11) is given. With B as a center, draw an arc cuttingthe sides of the angle at D and E. With D and E ascenters and a radius greater than half of arc DE, drawarcs intersecting at F. A line drawn from B throughpoint F bisects angle ABC.Two methods used to divide a line into a givennumber of equal parts are shown in figure 2-12. Whenthe method shown in view A is to be used, you willneed a straightedge and dividers. In using this method,draw line AB to the desired length. With the dividersset at any given radius, use point A as center and scribean arc above the line. Using the same radius and B ascenter, scribe an arc below the line as shown. FromFigure 2-10.—Laying out a drip pan with dividers.Figure 2-11.—Bisecting an arc.2-4

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