HAMMER, STEAM-HAMMER, a tool used for applying the force of impact, either for the purpose of beating malleable materials into a required form, or for driving nails, wedges, etc. The common hand-hammer consists of an iron head, usually faced with steel, fixed crosswise upon a wooden handle. When one side of the head is thinned out of a wedge form or to a point, this is called the pane of the hammer. The face is the flat disk which strikes the work. Carpenters' and joiners' hammers have a bent pane with a V-shaped notch, which is used as a bent lever for drawing nails, etc. The pane is sometimes sharpened so as to form an adze or chisel. A multitude of other modifications in the form of hammers are made to snit different kinds of work. Some of the more important of these are treated under the heads of the various operations, .such as FORGING, FILE-CUTTING, GOLD-BEATING, etc.
For many purposes, hammers are required of greater weight than a man can wield; and a great variety of power-hammers are used. These, for the most part, are masses of iron raised by steam or other power, and then allowed to fall by their own gravity upon the work. The helve or slsingling hammer, used for compressing the mass of iron drawn from the puddling furnace, and the tslt-hammer, used in the manufacturing of -shear-steel, are important examples of such hammers. The first is a heavy bar of cast iron about 10 ft. long, weighing 3 or 4 tons and upwards, to which is attached a head of wrought iron faced with steel, weighing pearly half a ton more. It works upon an axis at the end of the bar furthest from the head, and is raised by cams attached to a heavy wheel set in motion by steam or water-power; these cams strike i or "lick" a pro jection extending beyond the head, and thus raise it about 18 or 20 in. at the rate of from 70 to 100 times per minute. The tilt-hammer is similar, but much lighter, and is adapted for striking above 300 blows per minute. In order to obtain this velocity, a short " tail" extends with a downward inclination beyond the axis, and the cams strike this downwards, and thus lift the longer arm of the lever to which the head is attached.
These, when worked by steam. as they usually are in this country, are, of course, steam-hammers; but when the term steam-hammer is used without qualification, it applies to another and more elaborate machine of very different construction, invented by Mr. James Nasmvth in 1842, and subsequently modified and improved in some of its minor details. In this. the hammer is attached to the bottom of a heavy mass of iron, the "hammer-block," capable of rising and falling between upright bars or "guides;" this, again, to the rod' f a piston, works in a cylinder placed perpendicularly over the IttiminerLblock, hammer, and anvil. As the piston rises in the cylinder, it lifts the attached mass, which is then allowed to fall from varying heights,. according to an adjustment which can be made by au attendant simply touching a han dle. The adjustments are so perfect that it may be made to crush a mass of iron, and at the next blow to crack a nut held in the fingers without damaging either kernel or fingers, or to crack the top of an egg in an egg-cup, as might be done with the bowl of a spoon. The mechanism by which this is effected is too elaborate to be described here in detail. One novel contrivance, viz., the "latch," which reverses the action of the steam-valves at the precise moment required, is of remarkable ingenuity.
In the first " Nasmyths" that were used, the weight of the descending mass—viz., the hammer-block, hammer, etc.—was from 30 to 60 cwts., and they were justly regarded as mechanical marvels. Steam-hammers with a descending mass of 20 to 50 tons have since been constructed. In order to compare the power of these with the " helve" or other hammers, which descend by angular motion on a pivot, it must be remembered, that these latter, when formed of a straight bar, are only effective to the extent of a body of one-third of their weight falling directly from a corresponding height, ou account of the fact that the whole bar forming the hammer is moving with a velocity varying from nothing at the axis, to a maximum at the cud of the bar, where the hammer-face is fixed.