The burning should be commenced at the under side of the pipe, Fig. 31, and proceed both ways from the starting point and finish at the top. If the beginner has successfully overcome the difficulties of the seams preceding this he will find no trouble in making a strong and workmanlike seam on this pipe. Pipes are seldom used heavier than the grade known as D for this class of work, and for that reason it is seldom necessary to add lead to these seams. But if a hole should be burned in the pipe on the under side, lead should be added to the top side of the pipe and then made to follow the flame to the desired spot. This will be found a quicker and more certain method than attempting to add lead directly to the hole. A properly burned pipe should show the full thickness of the pipe when cut with a saw.
Fig. 31.—Burning a Butt Seam on Round Pipe.
Through Seam on Round Pipe.
Where heavy pipe that is to be used under pressure is to be joined it must be burned through to provide strength, and the ends prepared in the same way as just described, but the ends must also be trimmed off all the way around with a slight bevel reaching from the outside almost to the inside bore of the pipe. The bevel must stop so as to allow a narrow square butt end on each pipe. Then when a piece of paper has been placed on the inside to prevent lead running into the pipe, the two ends when butted will present a V-shaped groove, as shown in Fig. 32, reaching all around the pipe. The burning is commenced at the bottom, as shown in Fig. 31, and the two ends securely united. The groove is then filled by burning on additional lead from a thin cleaned strip until the groove is filled and the pipe made as heavy and strong at this point as anywhere on its entire length.
Fig. 32.—Joint Prepared for Through Burning.
The Lap Seam on Round Pipe.
Fig. 33.—Preparing for a Lap Seam.