Page:Sheet Metal Drafting.djvu/231

Rh In order to develop the patterns it is necessary to know the exact widths of these flat surfaces at each cutting plane, and in order to gain this information stretchouts must be made as shown by Figs. 307, 308, and 309.

Upon any vertical line a stretchout of the throat of Fig. 306 is made as shown by points O, N, M, K, H, and G of Fig. 307. Through each of these points perpendicular lines are drawn. Upon lines O and N one-half of the straight line in the oval profile must be laid down on each side of points and N. Straight lines