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.
This is a socket joint furnished with a contrivance, as shown in Fig. 148, to allow a length of metal piping freedom to expand and contract during the passage through it in almost immediate succession of hot and cold water. In the case of lead pipes a flange is soldered to the foot of the upper length, and an india-rubber ring inserted between it and the flange of the socket, with or without a packing of red lead and hemp in the cavity round the spigot. It must on no account be attached to inside or even to any unventilated soil-pipes, which when fixed outside a building should if possible run down a shady corner or other sheltered part to escape the ill effects of too great a range of temperature.
This occurs in lead rainwater pipes, vertical waste pipes, etc, the sockets being usually cast with ears and mouldings if required, and soldered on with the copper-bit. Generally, however, in lieu of a socket the tacks and astragals are soldered to the upper end of the lower pipe, and the lower end of the top pipe is reduced and inserted therein.
Soldered Joint is made when two metal pipes, sheets, parts, or pieces are united by means of a third substance called solder, which is a metal or alloy varying in kind and chosen for being more fusible than the metals united, and capable of combining readily with both. The soldered joints made by builders belong to the trades of the plumber, zinc worker, and gasfitter, and the solders employed by them are mixtures of lead and tin, and called "soft" solders, being so named because they melt at low temperatures, whilst the "hard" solders (described under Brazed Joint in Section XII., and used by the smith and coppersmith) melt only at a red heat. The soft solders are again divided into coarse and fine, the least fusible containing the most lead or the least tin being classed as coarse, whilst the most fusible or those containing a preponderance of tin are called fine solders. As lead and zinc when used as a roof-covering move under the influence of a change of temperature, no soldered joints are proper between sheets, though in minor parts, or in patching or effecting repairs, they are permissible. If one edge also of a sheet be left free the other may be soldered, but the necessity for this rarely arises, since the fixed edge is usually secured to a raglet or joint in masonry, or by means of "lead dots," and screws, if to woodwork, as noticed under Screw Joint, though nails with large heads may be used instead of screws. The lead lining to stone gutters is sometimes jointed together in lengths with solder, but the whole is left free. So good, however, was the masonry of the gutters in mediaeval buildings that no lead lining to them was necessary. The parts to which the solder is to cling are scraped clean with the shavehook and touched with tallow to prevent oxidation, and smeared with tallow as a flux, and are then run with the usual coarse and soft solder called pot metal or plumbers' solder, composed of 2 parts of lead and 1 of tin, which is smoothed down with the redhot iron and finished off by wiping, as more fully described under Wiped Joint. The connection between the outgo of lead traps and soil pipes ought invariably to be a wiped soldered one. "With fine solder consisting of 2 parts of tin to 1 part of lead, or these metals in slightly different proportions, resin is the flux used. The fusing points of lead, zinc, tin, and these varieties of coarse and fine solder are 617°, 773°, 451°, 446°, and 340° Fahr. respectively.