RIVETING, considered in its simplest form, is nothing more than the hammering of an iron bolt through a hole punched in two iron platen; but in the vast engineering operations of the present day, where rivets are used, not merely by the thousand, but by the million, the rapid and exact management of the operation become important matters. The Britannia tubular bridge over the Dlenai was the first of theme great examples of rivet•fastened plates ; the Great Eastern steam ship was a second ; and the Victoria railway bridge over the St. Lawrence, at Montreal, is a third. The rivets themselves may bo simply pieces cut off from iron rods, and heated in a forge to a state fit for hanunering ; hut under NAIL 3IANUFACTURE Will be found a notice of certain machines which are equally suited for making nails, rivets, Dam, and spikes.
At a meeting of the Institute of Mechanical Engineers, in 1857, Mr. Harvey ma]o the following observations on rivets and riveting : " In the manufacture of steam-boilers, the operation of riveting is mostly effected by hand-labour ; and in order to bring the heads of the rivets to a proper form and finish, much of the hammering takes place when the rivet has approached to a nearly cold state. The tendency of this is, to destroy, to a certain extent, the fibrous character of the rivet. The auto of a rivet-head, starting off under the operation of proving the boiler, although seldom occurring, has revealed the fact that a crystalline character must be more or less assumed by the iron in all rivets worked In the usual manner; and hence, besides arising at economy by the use of steam for riveting, it is very desirable that the rivets should be finished in as short a time as possible, and without that succession of blows by which the fibrous character of iron is always more or lees injured." In hand-riveting, it may be added, the head is made conical by the shape and action of the riveting hammer; whereas in steam-riveting the head becomes convex, which is better. Neverthelem, steam-riveting machines, though many have been invented, have not hitherto come much into use. Some are found to be too complex, and likely to get out of order. Some require a pres sure of steam of 50 lbs. on the square inch, with either a separate boiler
or a large steam-eylinder, which renders them too costly. Some have a defect arising from the peculiar mode in which they act ; a cam, moving through a fixed distance, and acting through a combination of levers, with a fixed distance for the travel of the riveting die, is unable to adapt itself to irregularities in the lengths of rivets which may occur in general work, and which must occur when rivets go sometimes through two, and at other times through three thicknesses of plates. Messrs. Whitelaw and Harvey have endeavoured to surmount some of these difficulties in a riveting-machine of recent introduction. The steam-cylinder is 15 inches in diameter by 21 inches stroke. A system of levers and eccentrics carry a shearer, a punch, and a die ; for the machine is intended to perform all three operations of cutting iron plates, punching holes in them, and then driving rivets into the holes. The machine is not wholly self-acting; it is momentarily stopped by hand after every stroke. The effective action of steam is upwards ; the downward movement is the effect of the weight of the moveable parts of the apparatus. Between the piston and the bottom of the cylinder a portion of the exhausted steam is retained as a cushion, to bring the piston softly to rest. Steam of 201b. to the inch has pressure enough for this machine. It has power to punch a hole three-quarters of an inch diameter through a cold iron plate three-quarters of an inch thick, and to effect the cutting and the riveting for the same plate. In riveting, the action upon the rivet-head is a pressure, not a blow ; this pressure becomes more and more intense as the process advances, until just before the head of the rivet is finally shaped, it amounts to something like 30 tons.
In riveting, whether by hand or by machine, it is necessary to furnish a pressure against one end of the rivet to assist the action at the other. In the hand method, one man holds a hammer forcibly against one end of the rivet in the hole, while another strikes the other end. In the machine method, the action•is like the pressure of a die and counterdie.