Suppose it is required to make a pan whose dimensions are 19 ½ in. by 13 ½ in. at top, 18 in. by 10 in. at bottom, and
2 in deep. Then the overhang of the sides will be -
13½ - 10 / 2 = 1¾ in.
And that for the ends -
19½ -18 /2 = ¾ in.
The lengths to add on to the bottom for the sides and ends can be calculated as in the previous case, or obtained by setting out as in Fig. 65. Two lines are drawn square to each other, and the depth of the pan marked up, and the two overhangs along, the lengths of the side and end being obtained from the slant lines. On the pattern it will be seen that these lengths are set out by making A B = a b and AD = ad. The overhang of the side must now be put on to the end and the overhang of the end added to the side. That is D C must be made 1¾ in. long and B E ¾ in. Now, if the setting out is done correctly so far, the lines A E and A C should be equal in length; hence this always gives a check as to the correctness of the work. In bending up, it should be remembered that the lines A C and A E coincide to form the corner, so that for the top of the pan to be level these must be the same length. Now to mark out the lines for the part to be cut away. Bisect the angle C A E by describing two arcs of circles with equal radius from the centres E and C, intersecting in H, thus obtaining the line II A. Decide now whether the flap has to be folded on the end or side, for whichever it has to be turned on will fix the angle of the top line of the flap. In this case the flap is arranged to be folded over on the end. With centre C, and any convenient radius, describe the arc P O N, then cut off O N equal to O P by drawing an arc with O as centre and O P as radius. Join C to N, and produce the line until it cuts A II in F. Join E to F, and thus the part to be cut away is determined. If the flap is to be folded on to the side of pan, then a similar construction will have to be gone through, commencing with point E. This is shown in dotted lines.
It will be seen that in the case of a pan of unequal taper the shape of the corner cut on the pattern depends upon whether the flap is to be turned over on to the side or the end, and if cut to suit one will not fit on the other. The shaded part on the pattern can be used for a template to mark the other corners, as in the previous case.