It is not necessary to be so particular on horizontal seams, as on seams in that position you are assisted by gravity. The lead drop that is melted from the upper lap cannot do otherwise than unite with the under lap. It must be remembered that in starting a seam you have cold lead to fuse, and after the first drop is started the lead in its vicinity will be heated almost to the melting point, and you will probably be surprised to see the lead run at the approach of the flame for the next application.
Do Not Hurry.
The point to be taught here is that you must not attempt to hurry this work or holes will surely be burned in the sheets, which oftentimes makes difficult work to patch. The old adage, “haste makes waste,” can well be applied to lead burning. Sufficient time must be allowed for one drop to set before attempting to place the next drop. Time spent on practicing at the bench is time well spent, as many little details that cannot be brought to the beginner's attention here will be learned in that way and stored in his mind for future application.
CHAPTER IX.
THE DIFFERENT KINDS OF SEAMS.
There are two kinds of seams proper, viz.: The butt seam and the lap seam. The butt seam is used principally for joining horizontal waste pipes and in lengthening traps, or for any purpose where it is desired not to have the point of junction show. This form of seam can be burned clear through—that is, the lead can be heated until fusion takes place nearly through the entire sheet. It is generally necessary to add lead to the seam if it is desired to make the seam as strong as the sheet it joins, unless the article to be burned is of such a size as to be possible to allow of its being burned on both sides, which makes the strongest of seams. The lead for the butt seams is prepared by rasping the edges of the lead sheet to be joined straight and true, Fig. 22, so that when the edges of the lead are brought together they will fit close its entire length. The edges are then shaved for a distance of ⅛ inch each side of the edge, making a seam ¼ inch wide. On stock heavier than 12-pound sheets the edge should be shaved off, making a deep V-shaped groove, and the seams must be made by adding lead. This allows the fusion to take place nearly through the sheet. The butt seam is the simplest form to burn, no matter in what position it is placed.
Fig. 22.—Rasping the Edges of the Lead Sheet Straight and True.
The lap seam is the seam commonly used, and as between the butt seam and the lap seam the latter is generally to be preferred. As it is not necessary to cut and trim the edges true, it dispenses with any additions of lead, except at rare intervals; it leaves the left hand free to handle the shave hook, and the lap can be dressed to fit any uneven spots. It also makes the next best seam to through fusing. By lap seaming a tank can be lined in about half the time required to butt seam the same article, which is an important item to the customer.
Fig. 23.—Burning a Lap Seam.