The hammer is a tool employed to deliver a blow, the force of which is augmented by the weight of the hammerhead. In every handicraft in which hammers are utilized, a number of special forms are employed; the carpenter, the mechanic, the mason, the coppersmith, the jeweler, the blacksmith, and numerous other craftsmen each employ several, and sometimes numerous, different types of hammer.
The application of power to the hammer was a most important advance. It was preceded by the use of hand-operated trip-hammers—hammers too heavy to be handled in the ordinary way, but pivoted about a point on the handle distant from the head, and worked by lifting the head and allowing it to drop. The steam engine, soon after its invention, was employed to operate these by means of cams and other devices, but the invention by Nasmyth, in 1839, of the steam hammer was the beginning of a new epoch, for it could be made to develop any required power, while at the same time the blow delivered could be regulated to a nicety. The steam hammer consists of nothing more than a vertical cylinder, in which a piston travels; the hammer-head is attached to the end of the piston rod. The steam is admitted below the piston and raises the hammer to any desired height. It is then allowed to fall, the force of the blow being greatest when its fall is hastened by steam admitted above the piston.
A very important modern tool is the pneumatic hammer, made in a large number of forms and weights for use in the hand. It is used for chipping work such as castings, corroded surfaces, and stone-work, for riveting and caulking. In many operations work can be done at three times the rate, and with less fatigue, than by the use of the hand hammer.