The making of a good sound riveted joint is one of the most important operations in plate metal work; hence in this chapter we intend to consider a few of the main points that should be taken into account in the designing of a properly-constructed joint. To design a riveted joint to give the best possible results with any given material for some particular purpose is not by any means a simple matter, and in the more complicated cases is somewhat outside the scope of a plater or boiler maker's work. We shall therefore deal only with the common forms of joints.
In the first place, it should be remembered that in ordinary practice it is never possible to make a riveted joint equal in strength to the solid plate, the relative strength of joint to plate varying from 50 to 90 per cent., according as to whether it is single, double, or treble-riveted, lapped or butted, punched or drilled, or iron or steel plates and rivets.
To increase the strength of the joint, it has been proposed to thicken up that part of the plate which forms the joint. Whilst theoretically there is no doubt but what this plan would give a joint equal in strength to the rest of the plate, practically it would not act on account of the cost and difficulty of rolling plates with thickened edges, and the awkwardness in their manipulation. In some cases welding is resorted to; but even in this, the uncertainty of the joint being welded right through makes it doubtful if a welded joint is, on the whole, any stronger than a riveted joint. For furnace plates there is not so much harm, as the joint here is in compression, whilst in the shell-plates the joints are, ,of course, in tension.