When using a hammer. to drive nails, it should be grasped firmly near the end of the handle. The hammer blows are delivered by a wrist-and-elbow motion rather than by moving the entire arm at the shoulder. When it is necessary to strike very heavy blows, the full arm can be brought into use. The hammer must be held at such an angle that the face will strike the nail squarely. If each blow does not meet the head squarely, the nail will be bent.
When starting a nail, the nail is held in place by the free hand, and then given several light taps with the hammer. The hand that was holding the nail should be taken away before actually driving the nail. Make certain that the nail is well started into the wood before using a full hammer blow. A nail that has not had sufficient start will fly out of the wood when struck with a hard blow. Nails and brads should not be driven in flush with the surface of the board without the aid of a nail set; otherwise hammer marks on the wood might result.
When pulling out nails, the claw is slipped under the head of the nail and the handle is pulled back to a vertical position. If this is not sufficient to remove the nail, a block of wood should be placed under the hammer head and the operation repeated. The block of wood will also protect the surface from which the nail is being drawn.
A hammer head should be held securely on the handle. If the head is loose the hammer should not be used, for then there is danger of the head's flying off. A hammer handle that is split is another source of danger, for a handle in such condition might break completely.
The face of the hammer should be clean and without nicks. Water, glue, oil, or grease on the face may result in the hammer's sliding off the work as a blow is struck. Rubbing the face of a hammer across a piece of sandpaper will remove glue.
The peen hammer
The peen hammer is widely used. The head is so shaped that one end, called the peen, can be used to produce dents or depressions or to set up tension in metal. When a hammer is so used, the process is called peening.
In the cross-section insert of figure above, note that the eye is made smaller on the side through which the handle is inserted. This is done so that when the wedge is driven, the wood in the eye can spread and so lock the handle in the head.
This wedge is generally made of soft steel and must always be tight. A mechanic accustomed to using hammers always looks to see that it is tight before he strikes a blow. He has learned to do this because a loose head may fly off and cause serious injury. Like many other useful tools, the hammer can be the cause of serious accident if improperly used.
When working in close quarters the first step should be to make a slow-motion trial stroke with the hammer. This is done to make sure that when the eye of the user is concentrated on the work, the hammer will not be deflected by some unnoticed object in its path.
A hammer which shows cracks in either head or handle should be kept in a locked container until it has been repaired or it should be immediately dismantled and junked. Failure to observe these simple rules may result in broken wrists or fingers, head injuries, or loss of eyesight.
In describing the construction of the hammer, peening was mentioned. In peening, the surface struck is either dented by the blow or if so supported that it cannot dent, a tension is set up which causes it to stretch. A sag is taken out of a saw by resting the convex side of the sag on the anvil and peening the other side with a ball-peen hammer. The stretching of the surface on the concave side causes the two surfaces to become parallel.
Whenever a metal surface is struck with a hard-faced hammer, the surface is either stretched or dented or both. Sometimes a piece of metal must be driven or bent without marring its surface. Two methods can be employed to accomplish this. One is to place or hold a piece of soft metal over the surface to be struck so that it will receive the blow. The other method is to use a soft hammer.
Hammers for driving pins are sometimes made of lead, copper, or an alloy such as Babbitt metal. Bending and forming hammers may be made of tightly rolled rawhide. There is a special type of mallet sometimes used for forming and bending. In this type, the body of the head may be made of wood or metal. The faces are made of material suitable to the purpose, such as rubber, fiber, soft metal, or plastic.
The nail set
A nail set is used in conjunction with the hammer to set nails and brads below the surface of the wood without marking or marring the wood with the face of the hammer. The sizes of nail sets range from 1/32" to 5/32”; they indicate the diameter of the tip. Different sized nail sets should be used for different sized nails, but in any case the tip of the nail set should be smaller in diameter than the head of the nail it is used on.
When a nail-set tip becomes flattened with use, the tool should be discarded, for it will no longer be capable of cutting into the head of a nail to prevent slipping. The head of a nail set should be kept square. From constant use, the head will burr over and become round.
The rounded head is likely to cause the hammer to slip off when striking a nail set, and the burred edge may be chipped off from the hammer blows. The chips broken off under such conditions have a considerable force behind them and may penetrate the hand holding the nail set. The burr can be removed and the head made flat by grinding.