In Fig. 32 another representative example of square pipe-jointing is given. The two pipes are of the same diameter, the branch fitting on to the main obliquely, with two of its flat sides parallel to the edges of the main pipe. It will be seen that it is also arranged so that a side of the branch pipe and an edge of the top pipe come together, such that the two pipes will lie flat against a wall.
After going carefully over the last case, there will be little need to give much explanation in this. The important points to notice being that the lengths 2 3 and 4 5 on the bottom line of branch-pipe pattern are obtained from 2' 3 in the end view, and also that the lengths 2' 3' or 4' 5' on the main-pipe pattern are measured from 2' 3' on the square, which is the end view of elevation on the main pipe. The lengths of lines for the branch-pipe pattern are, of course, measured in the usual way from the base line to the joint line, in this case (Fig. 32), as in the others, the numbered points on the pattern corresponding to those on the elevation of the joint' line. The various dimensions to fix the shape of the hole are shown projected as before.
It will be seen that the seam for the branch pipe is arranged to come down the centre of the side.
The patterns have been set out so that if the sheets are bent up as in the last case the pipes will come together properly. The settings-out in connection with the last two elbows are good examples of the geometry of sheet metal work as applied to flat surfaces; and whilst in themselves have not a very extended application, yet serve to illustrate some of the methods that can be used in plain surface work.