Page:Sheet Metal Drafting.djvu/152

over the hatchet stake, the corners taking the shape shown in the illustration. These corners are then closed down on the "square head."

Third Operation.—Each corner in turn is then placed in position on the "crooked square head" and the corner "brought around" as shown in the illustration.

Fourth Operation.—The wire edge is then "laid off" over the edge of the bench, the wire inserted, and finished in the wiring machine. The bottom edges are then straightened and the oval handles attached to the ends of the pan.

Laying out Directly upon the Metal.—Figure 188 shows the pattern of a dripping pan measuring 12⅜ in.×5⅜ in.×1 in. deep. The first step is to compute the size of the blank required. Since the bottom is 1¼ in. smaller than the top, the bottom measurements would be

${\begin{aligned}12{\frac {3}{8}}''-1{\frac {1}{4}}''&=11{\frac {1}{8}}''{\text{ (length)}}\\5{\frac {3}{8}}''-1{\frac {1}{4}}''&=~4{\frac {1}{8}}''{\text{ (width)}}\end{aligned}}$

To each dimension of the bottom must be added two slant heights and two wire edges. The slant height of a pan 1 in. deep and ⅜ in. flare is $\scriptstyle {1{\frac {1}{16}}}$ in.; therefore, the dimensions of the blank would be

${\begin{aligned}11{\frac {1}{8}}''+(1{\frac {1}{16}}\times 2)+({\frac {3}{8}}\times 2)&=14''{\text{ (length)}}\\4{\frac {1}{8}}''+1(1{\frac {1}{16}}\times 2)+({\frac {3}{8}}\times 2)&=~7''{\text{ (width)}}\end{aligned}}$

The workman cuts a rectangular piece of metal 7 in.×14 in. and lays off a ⅜-inch wire edge, Fig. 188. Inside of these lines he lays off a distance of $\scriptstyle {1{\frac {1}{16}}}$ in. to form the outline of the bottom. He then develops the pattern of one corner, according to the description given for Fig. 187. Having obtained the pattern for one corner, he transfers the measurements to the other three corners and the pattern is complete. The shaded portion of Fig. 188 denotes that part of the blank which is cut away.

61. Related Mathematics on Dripping Pans.—Dripping pans are made in a great variety of sizes, the more common of which are: 10″×15″×2¼″; 12″×17″×2¼″; 12″×19″×2½″; 14″×15″×2½″; and 18″×19″×2½″.

Problem 32A.—What will be the dimensions of the blanks required for each of the above sizes of pans?