Among the hand-tools there are a number of hammers that are common to most trades.

Therefore it is necessary to know the principles underlying their construction and use.

The small end of the hammer is called a peen, and "to peen" means to hammer lightly with the small end. Hammers are made of tool steel and tempered very hard on each end, the eye being left soft. The neck of the hammer handle is made small so that it will spring a little under the shock of the blow. The spring makes it less tiresome to use. The face of the hammer is made slightly crowning or rounding.

The claw hammer (Fig. 122) used principally for driving nails, is probably the most commonly used tool. It is based upon the principle of the lever. The hammer should not be grasped near the head but at the end of the handle, so that the greatest leverage may be utilized. To deliver a free, accurate blow, the wrist should be kept up so that the handle is horizontal when the blow falls. Claw hammers are graded by the weight of the head; the ordinary claw hammer weighs from 1/2 to 1 3/4 lbs.

Fig. 122.   Claw Hammer.

Fig. 122. - Claw Hammer.

Machinists' hammers for metal work are made in three forms as shown by Fig. 123. Fig. 123a represents a ball-peen hammer, the small end of which is shaped like a ball; Fig. 123b a straight-peen; and Fig. 123c a cross-peen hammer.

The sledge hammer, used many times every day by the blacksmith, is a tool so large and heavy that two hands are usually needed to wield it. Sledge hammers are also used for breaking coal, those designed for this purpose having a particularly long head. The heavy smooth-faced hammer, frequently used for driving wedges in splitting stone, is also referred to as a sledge hammer. The peen of a sledge hammer is usually made of steel.

There is still another hammer called a lead or copper hammer which is used for striking on finished parts that would be dented by a steel hammer. The machinist never uses a steel hammer on finished work. Other hammers used for special purposes are the chipping and riveting hammers.