This section is from the book "The New Metal Worker Pattern Book", by George Watson Kittredge. Also available from Amazon: The new metal worker pattern book.

In Fig. 311, let NCDO be the elevation of an elliptical pipe fitting against a roof, represented by A B. Let E F G Q be the section or profile of the pipe. Draw the profile in convenient proximity to the elevation, as shown, and divide it into any convenient number of equal parts. Place the T-square parallel to the sides of the pipe, and. bringing it against the points in the profile, drop lines cutting the roof line A B, as shown. Opposite to the end of the pipe, and at right angles to it, lay off a stretchout, as shown by H I, and through the points in it draw measuring lines in the usual manner. Reverse the T-square, placing it at right angles to the pipe, and. bringing it successively against the points in A B, cut the corresponding measuring lines, as indicated. A line traced through these points, as shown by K L. M, will be the required pattern. In the illustration the long diameter of the ellipse, or E G, is shown as crossing the roof. The method of procedure would be exactly the same if the pipe were placed in the opposite position - that is, with the short diameter Q F crossing the roof. In such case the profile should be turned so that Q F is across the roof, or parallel to C D. and the elevation duly projected from it. The pipe might with equal facility he placed so that the long diameter should lie at any oblique angle desired.

Fig. 311. - The Pattern of an Elliptical Pipe to Fit Against a Roof of One Inclination.

The New Meal Worker Pattern Book.

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