In [fig. 41] may be seen an example of zig-zag riveting.
Fig. 41.
Caulking.—By this is meant the closing of the edges of the seams of boilers or plates. In preparing the seams for caulking, the edges are first planed true inside and outside; and after the plates have been riveted together, the edges are caulked or closed by a blunt chisel about 1⁄4-inch thick at the edge, which should be struck with a 3 or 4-lb. hammer; sometimes one man doing the work alone and sometimes one holding the chisel and another striking.
Fullering a boiler plate is done by a round-nosed tool, while caulking is executed by a sharper instrument.
The thinnest plate which should be used in a boiler is one-fourth of an inch, on account of the almost impossibility of caulking the seams of thinner plates.
It is a rule well known to all practical boiler makers that the thinner the metal (compatible with due strength) the longer the life of the boiler under its varying stresses and the better the caulking will stand.
STEEL RIVETS.
Hitherto there has been some prejudice against steel rivets, and while this may have some foundation when iron plates are used, it is certainly baseless when steel plates are concerned. The United States government has clearly demonstrated this. All the ships of the new navy have steel boilers, riveted with steel rivets, and an examination of the character of the material prescribed and the severity of the tests to which it is subjected show that these steel-riveted steel boilers are probably the best boilers ever constructed.