Fig. 3069.

The shape of the cams, as c d, determines that of the work; thus in [Fig. 3069] is shown a pair of rolls for forming knife blades, each cam having sunk in it a die equal in depth to half the thickness of the knife.

If the work is very short in comparison with the circumference of the rolls, two, three, or more cams may be arranged around the circumference, making an equal number of forgings or impressions, as the case may be, at each revolution of the rolls.

In [Fig. 3067] is shown a nail-forging machine for producing, from strip iron, nails similar to hand-made, at rates varying from two to three hundred per minute, and lengths of from six to one inch, two nails being completed at each revolution of the driving shaft of the machine. The framing consists chiefly of a main casting, to which are fixed an upper frame, carriages for the driving shaft, and other details. The principal moving part is a heavy steel slide, deriving its motion from a crank pin with adjustable throw; this slide carries two shears, two gripping dies, and sundry indispensable appendages, to some of which it imparts motions for guiding the nails between the stages of cutting off and finishing.

The successive operations by which each nail is perfected are as follows:—

A piece of iron about six inches long, and of a width and thickness respectively of the finished nail, is inserted at a red heat to the feeder of the machine; a narrow strip is immediately cut off the lower side of the heated iron, and by the motion of the steel slide is carried to and pressed against a fixed die; while in this position another die rises at right angles and presses the partially formed nail against another fixed die. Thus the headless nail is firmly held on its four sides, and while in this position a lever, moved by a cam, and carrying a suitable tool, advances and forms the head, thus completing the nail. The return motion of the steel slide releases the nail, leaving it free to fall, but as its weight is not sufficient to insure this happening, a “knocker off” is provided, which at the right moment forcibly ejects the nail by way of a guiding shoot into a receptacle placed outside the machine. It is to be noted that the tools for shearing and gripping, and which have to be changed with each different size of nail, are made of a special mixture of cast iron. They are thus easy of preparation and renewal, while at the same time answering their intended purpose as well as or better than the finest cast steel, at less than half the cost. The whole of the machine is carried upon an open-top cast-iron water tank, serving as a receptacle for the tongs and tools heated in withdrawing the iron from the furnace.

[Large
image
(110 kB).]