Chap. XIII.

TOOLS AND MACHINES.

1035

travelling table, and supported on the notched bar n: holes are now punched in plates ofsheet iron or copper with great accuracy and rapidity.

Fig. 1585.

PUNCHING BOILER PLATES.

Punching Holes in plates of wrought-iron and copper: in experiments made with a cast-iron lever 11 feet in length, when the strain was multiplied ten times by means of a screwand counterpoise, the following results took place : —

The sheets to be punched having been placed between two perforated steel plates, thepunch was introduced with a perfectly fiat face, and then forced by the pressure of thelever. The punch was £ inch in diameter, and through plates of iron *03 of an inch inthickness, it required a power of 6025 pounds; through one of ‘17 inches in thickness,

Fig. 1586.

PUNCHING BOLES,

11,950 pounds; and another of *24 inches in thickness 17,100 pounds: through a copperplate *08 inches in thickness 3983 pounds, and *17 inches in thickness 7883 pounds.

The power required to punch holes of different diameters through metals of variousthickness is directly as the diameter of the holes and the thickness of the metal.

A plate 1 inch in thickness and having holes an inch in diameter being taken as unitfor a calculation, we shall have 150,000 as the constant number for wrought-iron plates, and96,000 for those of copper. These constant numbers being multiplied by the givendiameter in inches, and then by the thickness in inches, the product will give the pressurein pounds, which is required to punch the hole.

Riveting Machines now perform the work which usually required three men, the holderon, or the one who placed the hammer against the head of the rivet, and two others, whobeat out the iron to the conical form given to its opposite end: the noise which ac-companied this operation is now entirely prevented. The motion is given to the machineby a leather strap, which communicates with both a tight and loose rigger; the speed isprevented from being too rapid by a pinion and large spur-wheel; as the pinion makes sixrevolutions, that on which the large wheel is hung, and also the cam, revolve but once.

The riveting lever rises and falls by the action of the cam, the face of which is steeled :at the lower end of the lever is a steel roller, which is turned as often as the cam worksagainst it: this materially obviates the friction, which would otherwise be very considerable.The riveting lever moves on a fulcrum, and is connected to the riveting tool by two shortlinks; this is kept at its work in a true and horizontal position by sliding backwards andforwards in a socket bearing.

The riveting block, in the form of a frustum of a cone, is placed on the sole plate,which receives the side framing: when the work is performed, the rivet is placed in thehole prepared for it by the punching machine : the machine is then put in motion by