When the two pipes are of the same diameter, very little more difficulty will be experienced with the patterns than in the last case. An elevation of the two pipes is first drawn (Fig. 30), making the required angle with each other, the lines A B and A C representing the diameters and the line B C the diagonal of the pipes.
The pattern for the branch pipe is set out by laying down four widths, each equal to A B, to make up the girth of pipe. To form the cut at top of pattern the lengths of lines are taken from the elevation. Thus lines B D and C E on the pattern are respectively equal to the lines with the same letters in the elevation. The three remaining lines O O are measured off the same length as the centre line O O on the pipe. The pattern is marked out so that the seam on the branch pipe will come on a side edge.
The shape of the hole can be determined from the pattern, the right-hand side being used to mark out that part of the hole, and the left-hand side the remaining part. The hole can, of course, be set out directly from the elevation, as seen in Fig. 30, the lettered lines of the hole corresponding in length to those with the same letters on the elevation.