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Rh depth of the rim plus an allowance of ¼ in, for the wire edge, and in. for a single edge, A 1-inch lap for riveting must be added to the length. This lap must be so notched that it will not interfere with the wire, which is placed in position before the rim is formed into a cylinder.

Pattern for the Handle.—Any straight line, Fig, 122, may be used as a line of stretchout. The profile of the handle, Fig, 122, is divided into equal parts and the divisions lettered A, B, C, etc. These divisions are transferred to the line of stretchout. Perpendiculars to the line of stretchout are erected at points A, B, K, and M. Distances of ½ in. and ¼ in. are set off on lines B and K, on each side of the line of stretchout. These intersections are connected by straight lines to form the body of the pattern. Lines A and M set off that part of the handle that laps and rivets to the cover, and should be notched as shown in Fig, 122. Rivet holes are located in the exact center of these laps.

40. Related Mathematics on Pitch Top Cover.—Problem 20A.—How much would 50 cone tops, shown in Fig. 118 (no rims or handles), weigh if made from No. 26 galvanized steel (.9062 lb. per square foot)? Add 25 per cent for waste.

Problem 20B.—What would be the weight of the cone top of a cover to fit over a 14" garbage pail? Allow ½" clearance between pail and cover on all sides, making the diameter of the base of cone 15", and the slant height 9". Cover to be made of No. 26 galvanized steel.