Riveting.—There are four descriptions of riveting, namely:
(1) Hammered or hand riveting.
(2) Snapped or set.
(3) Countersunk..
(4) Machine.
For good, sound work, machine riveting is the best.
Snapped riveting is next in quality to machine riveting.
Countersunk riveting is generally tighter than snapped, because countersinking the hole is really facing it; and the countersunk rivet is, in point of fact, made on a face joint. But countersinking the hole also weakens the plate, inasmuch as it takes away a portion of the metal, and should only be resorted to where necessary, such as around the front of furnaces, steam chests or an odd hole here and there to clear a flange, or something of that sort.
Hammered riveting is much more expensive than machine or snapped riveting, and has a tendency to crystallize the iron in the rivets, causing brittleness.
In the present state of the arts all the best machine riveters do their work by pressure, and not by impact or blow.
The best machines are those of the hydraulic riveting system, which combines all of the advantages and avoids all the difficulties which have characterized previous machine systems; that is to say, the machine compresses without a blow, and with a uniform pressure at will; each rivet is driven with a single progressive movement, controlled at will. The pressure upon the rivet after it is driven is maintained, or the die is retracted at will.
FIG. 17.