Page:Sheet Metal Drafting.djvu/147

Rh bear the numbers 9, 8, 7, 6, and 5½ as shown in Fig. 185. Measuring lines are drawn through each of these points. The distances a, b, c, etc., are taken from lines, a, b, c, d, and e of Fig. 183 and are set off on the measuring line. A curved line passing through these points will give the shape of the opening for the main part of the flange that is to fit over the ridge. The distance 10–M, Fig. 185, is made equal to 10–N of Fig. 183. A perpendicular is drawn at point M. The distance MN is made equal to 10–N of Fig. 182. Another perpendicular line is erected at point N. Distance NF is made equal to NF of Fig. 183. The bending line FG is drawn in. With F as a, center, arcs are drawn from points H, J, and K to the left an indefinite distance. With G as a center, the distance GH is set off on the other side of point G. Similarly, the distances GJ and GK are set off on the other side of point G. The straight lines KF and KJ will complete the pattern of one side of the flange, with the exception of the curve JHG. The other half of the pattern is exactly equal to the one already drawn and is produced by the same method.