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 formed by means of a cast iron shoe or chair, which is a medium of uniting beams, or rods, or rafters to walls, columns, or overhead girders, and struts to suspending rods, etc. It constitutes as characteristic a joint as that produced by a hinge, and singularly enough their analogy or affinity is even closer than that arising from the similarity resulting from the interposition of a metallic body between the parts connected, for shoes themselves are sometimes hinged when fixed over columns supporting railway bridges, etc, in order that the girders may transmit their load down the axes of the columns. Other remarks concerning shoes have been included in the description given of Cottered Joint.
Single Riveted Joint is made when two plates are united by a single row or file of rivets. The joint may be a lap between two main plates, or a cover in which each main plate is attached to one or two cover plates by one file only. In a single riveted lap joint in which the rivets have a diameter equal to two thicknesses of the plate, and where the lap and pitch are both three diameters, which is the best arrangement for uniformity of strength throughout the joint, the strength of the joint is only 52 per cent, that of the plate. A single riveted butt joint with a cover plate on only one side has likewise the same proportionate strength, but when there are two cover plates the rivets offer a double shearing area, or, in other words, are in double shear, and their diameter can accordingly be reduced to 1⅛ the thickness of the plate, the pitch to 3 ⅛ diameters, and the lap to 3, in order to obtain similar equivalent strength.
The variety formed by the union of a spigot and socket is described under that name and Pipe Joint as well. The tops of iron piles carrying columns are provided with sockets of octagonal form exteriorly for screwing in, but with circular apertures for receiving the feet of the overhead columns, which are secured therein with iron wedges and iron cement or other approved material.
Soft and hard solders are used for iron as well as for metals generally, with or without rivets, fractured cast iron even being made in some instances as strong as ever if properly tinned. For further particulars respecting the application of soft solder to iron see Copper-bit Joint in Section X. Hard soldering is sometimes effected as follows: - The surfaces to be united are filed clean, and, if heavy, bound together with steel, a thin strip of sheet copper or brass being laid over the joint and tied on with wire. A band of clay, free from sand, about an inch thick and 10 in. wide, is placed over the joint, and the whole laid near a fire, so that the clay may slowly dry, after which it is held before the blast and brought to a white heat. It must be allowed to cool slowly if the junction is between steel pieces, but on the contrary if between iron ones cooling off in water is necessary. The vitrified clay is finally broken away and the surface cleaned off. See also Brazed Joint, Section XII.