Some very peculiar jobs occasionally turn up in the way of connecting pieces. A simple but interesting example of this is shown in Fig. 37, in which two rectangular pipes are lying along the corner of a room, one fitting broadside, and the other with the narrow side on the same wall. The problem is to make a connecting pipe to join together the ends of the pipes. The pattern for this can be set out on the plate or sheet from the dimensions; but it will, perhaps, add clearness to the description to have a plan and elevation before us, as shown in Fig. 38. In striking out the pattern all that is necessary to use will be the square and measure. Let us suppose that the seam is to run down the back corner. Draw the line A B, and make it equal in length to the depth of the connecting pipe. Run up perpendiculars A C and B D, cutting these off equal to the width and length of the pipe section respectively. Draw C E G and D F H square to C D, and cut off to the pipe dimensions, as shown. Draw H L and G K parallel to B D or A C, and set along them the two dimensions of pipe, as seen on the figure.
In large work, where it might be awkward to draw the lines parallel, as explained above, a simple method, giving the same result, would be to describe a semicircle on the line G H, and then with centre G and radius equal to 18 - 6 = 12 in. mark the point N. The remainder of the construction can then be completed without trouble. Allowances to cover the particular method of jointing adopted must be added to the net pattern.
In shaping the plate, care must be taken to bend it in the right direction. In Fig. 38, if the ends of the plate are bent up, the connecting pipe will come into the correct shape and fit into position as seen in Fig. 37.