The sheet metal worker is so often called upon to make all sorts of pans that a consideration of the different kinds of corners that can be formed will not be here out of place. The unprofessional workman, too, occasionally wants to make a pan to hold some odds and ends that are lying about the bench or shop, and he should find no trouble in forming the simpler kinds of corners as explained in this chapter.
The strongest kind of pan corner that can be formed is probably that known as a "double lap," a sketch of which is shown, and also the pattern, in Fig. 58. The pattern for one corner only is given, as the setting out for each corner will be exactly the same. On account of the double lap it will be seen that there are two thicknesses of sheet metal at the corner, one of the laps being turned inside the pan and the other outside. The only marking out that is necessary is to add the depth of the side, on to the size of the bottom, the corner or diagonal line being cut along as indicated. It is a good plan to cut the points off the flaps as shown by the shaded part. If made of light tinplate, the flaps can be soldered down after the sides are bent up, and if of strong sheet iron, riveted as seen in the sketch. Without the iron is very strong, such as 16 or 14 gauge, there is no need to put holes in the plate before bending, as the rivets can be drawn right through with the upset, as explained in Chapter XXXV (Sheet Metal Joints).
In Fig. 59 the same method of jointing the corners as just explained is followed; but in this an edge is folded over along the top of the pan and used for gripping the two flaps, besides strengthening the edge of the sides. If the edge is also left on the flaps, one can be turned under and the other over the side edges, as seen in the sketch. There is no need to rivet this corner, or even to solder it, without the pan is required to hold a liquid.
Fig. 60 shows a pan corner that is formed by bending over a single lap and riveting. Allowance is made on the pattern for an edge to fold over all round the top of the pan. The corner of the plate will be cut away, as seen by the shaded part on the pattern. If the top of the pan is to be wired, it will be as well to notch the lap slightly larger, as seen by the dotted line. Holes for rivets, if required, will be punched in the plate, as shown on the the pattern.
A pan with a knocked-up corner is illustrated by Fig. 61. In cutting the corner of the pattern, care should be taken that a single edge is allowed on one side, and a double edge on the other. If the pan is to be wired along the top edges then notice must be taken that the laps are properly notched before bending. If the knock-up is required to be on the inside of the pan instead of the outside, then the edges for the knock-up should be folded over in the reverse direction, so that the double edge will come on the inside of the pan.
The pan corner sketched in Fig. 62 shows the method of doubling up the sheet metal to form a solid, or what is sometimes called a "pig's-ear" corner.
Pan corners 81
If it is required to form a pan with the sides square to the bottom, without wire or edge around the top, then there will be no need to cut the pattern at all, the corner being formed by bending along the dotted lines, as shown on the pattern.
All the above methods of forming a pan corner are applicable to pans having sloping or tapered sides, the various allowances for jointing being put on after the net pattern is marked out, as explained below.