# Hammer

For other uses, see Hammer (disambiguation).
Types A modern claw hammer Hand tool Construction

A hammer is a tool meant to deliver an impact to an object. The most common uses for hammers are to drive nails, fit parts, forge metal and break apart objects. Hammers are often designed for a specific purpose, and vary in their shape and structure. The term "hammer" is also used for some devices that are designed to deliver blows, e.g., the caplock mechanism of firearms.

The hammer is a basic tool of many professions. The usual features are a handle and a head, with most of the weight in the head. The basic design is hand-operated, but there are also many mechanically operated models, such as steam hammers, for heavier uses.

## History

The use of simple hammers dates to about 2,600,000 BCE[1][2] when various shaped stones were used to strike wood, bone, or other stones to break them apart and shape them. Stones attached to sticks with strips of leather or animal sinew were being used as hammers with handles by about 30,000 BCE during the middle of the Paleolithic Stone Age.[citation needed]

The hammer's archeological record shows that it may be the oldest tool for which definite evidence exists of its early existence.[1][2]

## Designs and variations

The parts of a hammer are the face, head (includes the bell and neck which are not labelled), eye (where the handle fits into), peen (also spelled pein and pane). The side of a hammer is the cheek and some hammers have straps extending down the handle for strength. Shown here are: A. Ball-peen hammer B. Straight-peen hammer C. Cross-peen hammer.
The claw of a hammer is frequently used to remove nails.

A large hammer-like tool is a maul (commander, beetle), a wood or rubber headed hammer is a mallet, and a hammer with a cutting blade is usually called a hatchet.

The essential part of a hammer is the head, a compact solid mass that is able to deliver the blow to the intended target without itself deforming. The opposite side may have a ball shape, as in the ball-peen hammer and the cow hammer (sometimes used for livestock slaughter, but now disparaged for animal cruelty). Some upholstery hammers have a magnetized face, to pick up tacks. In the hatchet, the hammer head is secondary to the cutting edge of the tool.

The impact between steel hammer heads and the objects being hit can create sparks, which may ignite flammable or explosive gases. These are a hazard in some industries such as underground coal mining (methane gas), or in other hazardous environments such as petroleum refineries and chemical plants. In these environments, a variety of non-sparking metal tools are used, primarily aluminium or beryllium copper hammers.[3]

In recent years, the handles have been made of durable plastic or rubber, though wood is still widely used.

Popular hand-powered variations include:

### Mechanically-powered hammers

Mechanically-powered hammer

Mechanically-powered hammers often look quite different from the hand tools, but nevertheless most of them work on the same principle. They include:

In professional framing carpentry, the manual hammer has almost been completely replaced by the nail gun. In professional upholstery, its chief competitor is the staple gun.

## Physics of hammering

### Hammer as a force amplifier

A hammer is basically a force amplifier that works by converting mechanical work into kinetic energy and back.

In the swing that precedes each blow, a certain amount of kinetic energy gets stored in the hammer's head, equal to the length D of the swing times the force f produced by the muscles of the arm and by gravity. When the hammer strikes, the head gets stopped by an opposite force coming from the target; which is equal and opposite to the force applied by the head to the target. If the target is a hard and heavy object, or if it is resting on some sort of anvil, the head can travel only a very short distance d before stopping. Since the stopping force F times that distance must be equal to the head's kinetic energy, it follows that F will be much greater than the original driving force f — roughly, by a factor D/d. In this way, great strength is not needed to produce a force strong enough to bend steel, or crack the hardest stone.

### Effect of the head's mass

The amount of energy delivered to the target by the hammer-blow is equivalent to one half the mass of the head times the square of the head's speed at the time of impact ($E={mv^2 \over 2}$). While the energy delivered to the target increases linearly with mass, it increases quadratically with the speed (see the effect of the handle, below). High tech titanium heads are lighter and allow for longer handles, thus increasing velocity and delivering more energy with less arm fatigue than that of a steel head hammer of the same weight.[8] As hammers must be used in many circumstances, where the position of the person using them cannot be taken for granted, trade-offs are made for the sake of practicality. In areas where one has plenty of room, a long handle with a heavy head (like a sledge hammer) can deliver the maximum amount of energy to the target. It is not practical to use such a large hammer for all tasks, however, and thus the overall design has been modified repeatedly to achieve the optimum utility in a wide variety of situations.

### Effect of gravity

Gravity exerts a force on the hammer head. If hammering downwards, gravity increases the acceleration during the hammer stroke and increases the energy delivered with each blow. If hammering upwards, gravity reduces the acceleration during the hammer stroke and therefore reduces the energy delivered with each blow. Some hammering methods, such as pile drivers,[specify] rely entirely on gravity for acceleration on the down stroke.

## War hammers

Main article: War hammer

A war hammer is a late medieval weapon of war intended for close combat action.

## Symbolic hammers

The hammer, being one of the most used tools by Homo sapiens, has been used very much in symbols and arms. In the Middle Ages it was used often in blacksmith guild logos, as well as in many family symbols. The hammer and pick is used as a symbol of mining. A well known symbol with a hammer in it is the Hammer and Sickle, which was the symbol of the former Soviet Union and is very interlinked with Communism/Socialism. The hammer in this symbol represents the industrial working class (and the sickle the agricultural working class). The hammer is used in some coat of arms in (former) socialist countries like East Germany. Similarly, the Hammer and Sword symbolizes Strasserism, a strand of National Socialism orientated toward the working class.

The gavel, a small wooden mallet, is used to symbolize a mandate to preside over a meeting or judicial proceeding, and a graphic image of one is used as a symbol of legislative or judicial decision-making authority.

In Norse Mythology, Thor, the god of thunder and lightning, wields a hammer named Mjölnir. Many artifacts of decorative hammers have been found, leading modern practitioners of this religion to often wear reproductions as a sign of their faith.

Judah Maccabee, "The Hammer".

In American folkore, the hammer of John Henry represents the strength and endurance of a man.

The hammer in the song If I Had a Hammer represents a relentless message of justice broadcast across the land. The song became a symbol of the American Civil Rights movement.