This section is from the book "A Practical Treatise On The Joints Made And Used By Builders", by Wyvill J. Christy. Also available from Amazon: Practical treatise on the joints made and used by builders.
Screw Joint is used in attaching lead covering to boarding, etc, with wood screws. Sinkings are made in the wood where the screws are to go, the lead is dressed down into them, and one or more screws are driven home. Their heads consequently lie in small hollows, and these are filled with molten solder wiped flush with the general surface. The patches of solder are called lead dots, and preserve the screw heads from oxidation.
Seam Joint is a mode of uniting the edges of sheets of plumbers' joints. 203 metal by means of a seam with, or without a lap or fold. In the latter case solder is necessary. A seam joint between two sheets of lead without a roll is formed by turning up the adjacent edges unequally so as to admit of one being bent down over the other. When this is done they are both turned or folded and dressed down close together flat to the surface and the joint is completed, but it is not equal to the roll joint either in neatness or security. When the plumber forms pipes of large diameter out of sheet lead the seam is soldered either with a copper-bit or red-hot iron. In both cases the edges are planed true, the lead rolled round a wood core, and the edges brought together and soiled, shaved, and "touched" or greased with tallow to prevent retarnishing. If the seam is to be made with the copper-bit, it is done with or without soil, and according to the usual method adopted when using that tool, as already described. When, however, it is made with molten solder and the iron, the solder is poured on with the right hand so as to cover about a foot in length and left floating, whilst with the left hand the plumber draws the red-hot iron along each side of the seam and cuts off the surplus solder. He then proceeds with another short length in the same way, an assistant in the meantime pouring or swabbing with a sponge a little water on the finished part to cool the solder and keep it from opening. This operation is sometimes called drawing lead pipe, but it is not to be confounded with that of making pipe by pressing or forcing lead through an orifice provided with a central mandril by means of a hydraulic press, nor with the older method of drawing cast lead pipes through a series of openings in steel plates to reduce them to the required thickness, and from which the term drawn pipe has originated.
A round wiped soldered pipe joint of which the length is rather less than the breadth.
Slip Joint is made by inserting the end of a lead pipe into an iron soil-pipe, for instance, of larger bore with a tight packing of red load and hemp between them, and a stout india-rubber band, 3 in. or 4 in. broad, surrounding the joint on the outside. This joint also admits of being stopped with molten lead or iron cement, but it then ceases to be movable. Slip joints undefended by traps have been fruitful in causing ill-health, if not mortal sickness, but when traps exclude sewer gas no pernicious effects appear to be due to them, for such joints occur between the flanged necking of a w.c. apparatus and the D trap below it, the pipe of the trap being dressed back upon the floor, or otherwise as considered expedient.