Page:Sheet Metal Drafting.djvu/136

122 arc drawn from the apex as a center, with a radius equal to the distance from the apex to the top of the spout, will complete the pattern. A -inch flange is added outside of the miter cut, as shown in Fig. 167, and a ¼-inch lap parallel to one side of the spout is also added.

Pattern of Body.—The pattern for the body is a rectangular piece of metal the length of which is equal to Diameter×π+½in., and the width of which is equal to the height of the can plus ⅜in. for the wire edge, plus ⅛in. for the single edge at the bottom of the can. This feature of the problem is so familiar to the student that it is omitted from the drawing. Manufacturers generally punch a round hole at the point where the center line of the spout intersects the side of the can. The hole may, however, be developed according to the principles laid down in Chapter V.

The Breast.—The breast is a portion of a cylindrical surface cut by two inclined planes. The top line of the breast in Fig. 165 is extended indefinitely to the left. At right angles to this line another line is drawn to serve as a center line for the half-profile. The line H-K is drawn at right angles to the center line. This line, if prolonged, should pass through the intersection of the breast and the top of the can. A distance equal to one-half the diameter of the can is set off upon H-K. The connecting points P and K of the half-profile should be drawn. The center from which this arc is drawn should fall on the center line of the half-profile. The arc is divided into four equal spaces. Extension lines are carried with the elevation of the breast as shown. A line of stretchout is drawn and the spacing of the half-profile with letters to correspond is transferred to it. From each intersection of the miter lines, extension fines are carried over into the stretchout. Starting from the half-profile, each extension line can be traced first to the miter lines and thence to a correspondingly lettered line in the stretchout. Curved lines passing through these points will give the half pattern of the breast. Fig. 168. A ¼-inch lap is added to the side that adjoins the body, and a ⅜-inch wire edge to the other side of the breast.

The Handle.—The handle or bail of the can is a straight piece of metal 1¼ in. wide that is formed to the profile shown in Fig. 169. The handle extends down below the top of the can and is riveted and soldered to the body. A double hem or a wire may be used to stiffen each edge of the handle. A boss is soldered into the upper