The direct application of steam to forging-hammers is without doubt the greatest improvement that has ever been made in forging machinery; not only has it simplified operations that were carried on before this invention, but has added many branches, and extended the art of forging to purposes which could never have been attained except for the steam-hammer.

The general principles of hammer-action, so far as already explained, apply as well to hammers operated by direct steam; and a learner, in forming a conception of steam-hammers, must not fall into the common error of regarding them as machines distinct from other hammers, or as operating upon new principles. A steam-hammer is nothing more than the common hammer driven by a new medium, a hammer receiving power through the agency of steam instead of belts, shafts, and cranks. The steam-hammer in its most improved form is so perfectly adapted to fill the different conditions required in power-hammering, that there seems nothing left to be desired.

Keeping in view what has been said about an elastic connection for transmitting motion and power to hammers, and cushioning the vibratory or reciprocating parts, it will be seen that steam as a driving medium for hammers fills the following conditions:—

First.—The power is connected to the hammer by means of the least possible mechanism, consisting only of a cylinder, a piston, and slide valve, induction pipe and throttle valve; these few details taking the place of a steam-engine, shafts, belts, cranks, springs, pulleys, gearing, in short, all such details as are required between the hammer-head and the steam-boiler in the case of trip-hammers or crank-hammers.

Second.—The steam establishes the greatest possible elasticity in the connection between a hammer and the driving power, and at the same time serves to cushion the blows at both the top and bottom of the stroke, or on the top only, as occasion may require.

Third.—Each blow given is an independent operation, and can be repeated at will, while in other hammers such changes [110] can only be made throughout a series of blows by gradually increasing or diminishing their force.

Fourth.—There is no direct connection between the moving parts of the hammer and the framing, except lateral guides for the hammer-head; the steam being interposed as a cushion in the line of motion, this reduces the required strength and weight of the framing to a minimum, and avoids positive strains and concussion.

Fifth.—The range and power of the blows, as well as the time in which they are delivered, is controlled at will; this constitutes the greatest distinction between steam and other hammers, and the particular advantage which has led to their extended use.

Sixth.—Power can be transmitted to steam-hammers through a small pipe, which may be carried in any direction, and for almost any distance, at a moderate expense, so that hammers may be placed in such positions as will best accommodate the work, and without reference to shafts or other machinery.

Seventh.—There is no waste of power by slipping belts or other frictional contrivances to graduate motion; and finally, there is no machinery to be kept in motion when the hammer is not at work.

Keeping these various points in mind, an apprentice will derive both pleasure and advantage from tracing their application in steam-hammers, which may come under notice, and various modifications of the mechanism will only render investigation more interesting.

One thing more must be noticed, a matter of some intricacy, but without which, all that has been explained would fail to give a proper idea of steam-hammer-action. The valve motions are alluded to.

Steam-hammers are divided into two classes—one having the valves moved by hand, and the other class with automatic valve movement.

The action of steam-hammers may............