Page:Sheet Metal Drafting.djvu/85

Rh measuring lines of the stretchout should be drawn. Starting at point 1 of the front elevation profile, the extension line is to be followed to the developed miter line, and thence to a correspondingly numbered measuring line in the stretchout. This intersection should be marked with a small circle. All the other points in the profile of Fig. 102 are traced in like manner, and the intersections for each measuring line in the stretchout determined. A curve traced through these intersections will give the miter cut of the pattern.

Opening in Main Pipe.—A line of stretchout, Fig. 104, must be drawn at right angles to the main pipe. The spacing of the apparent miter line is to be set off upon this line. These divisions are lettered to correspond to those of the apparent miter line. Fig. 101. Measuring lines, at right angles to the line of stretchout, are drawn from each point. The intersections of the developed miter are lettered as shown in Fig. 102. The position of the letters must be changed in the same way as the numbers in the profiles of Figs. 96 and 97. A line should be dropped from the point E of the developed miter line until it intersects the line E of the stretchout in Fig. 104. The intersection of the two lines is marked with a small circle. In like manner, intersections for each division of the developed miter line, as shown in Fig. 102, can be located. A curve traced through these intersections will give the true shape of the opening in the main pipe.