HAMMER, a tool used for applying the force of impact, either for the pur pose 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 on a wooden handle. When one side of the head is thinned out to 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 adz or chisel. There are also many other modifications in the form of hammers.
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 on the work. The "helve" or "shingling" hammer, used for com pressing the mass of iron drawn from the puddling-furnace, and the "tilt" hammer, used in the manufacture of shear-steel, are important examples of such hammers. The tilt hammer is sim ilar, but much lighter, and is adapted for striking more than 300 blows per min ute. These, when worked by steam, as
they are usually, are, of course, steam hammers ; and when the term steam ham mer is used without qualification it ap plies to a more elaborate machine of very different construction, invented by James Nasmyth, 1842, and subsequently improved in 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, is fixed to the rod of a piston, which works in a cylinder placed perpendicu larly over the hammer-block, 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 an attendant simply touching a handle. The adjust ments 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 ker nel or fingers.