thumb|right|upright=1.3|A modern [[claw hammer suited to drive and remove nails]]

thumb|Cartwheel [[mallets with heads of felt held between steel washers for use with timpani drums]]

thumb|Detail of the head of a [[war hammer]]

thumb|right|A [[geologist's hammer used to break up rocks, as seen in archaeology and prospecting]]

A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as with a forge), or to crush rock. Hammers are used for a wide range of driving, shaping, breaking and non-destructive striking applications. Traditional disciplines include carpentry, blacksmithing, warfare, and percussive musicianship (as with a gong).

The modern hammer head is typically made of steel which has been heat treated for hardness, and the handle (also known as a haft or helve) is typically made of wood or plastic.

Ubiquitous in framing, the claw hammer has a "claw" to pull nails out of wood, and is commonly found in an inventory of household tools in North America. Other types of hammers vary in shape, size, and structure, depending on their purposes. Hammers used in many trades include sledgehammers, mallets, and ball-peen hammers. Although most hammers are hand tools, powered hammers, such as steam hammers and trip hammers, are used to deliver forces beyond the capacity of the human arm. There are over 40 different types of hammers that have many different types of uses.

The high elasticity of the steel head is important in energy transfer, especially when used in conjunction with an equally elastic anvil.

In terms of human physiology, many uses of the hammer involve coordinated ballistic movements under intense muscular forces which must be planned in advance at the neuromuscular level, as they occur too rapidly for conscious adjustment in flight. For this reason, accurate striking at speed requires more practice than a tapping movement to the same target area. It has been suggested that the cognitive demands for pre-planning, sequencing and accurate timing associated with the related ballistic movements of throwing, clubbing, and hammering precipitated aspects of brain evolution in early hominids.

History

The use of simple hammers dates to around 3.3 million years ago according to the 2012 find made by Sonia Harmand and Jason Lewis of Stony Brook University, who while excavating a site near Kenya's Lake Turkana discovered a very large deposit of various shaped stones including those used to strike wood, bone, or other stones to break them apart and shape them. The first hammers were made without handles. 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. The addition of a handle gave the user better control and less accidents. The hammer became the primary tool used for building, food, and protection.

The hammer's archaeological record shows that it may be the oldest tool for which definite evidence exists.

The hammer head may be surfaced with a variety of materials including brass, bronze, wood, plastic, rubber, or leather. Some hammers have interchangeable striking surfaces, which can be selected as needed or replaced when worn out.

Designs and variations

thumb|The parts of a hammer are the face, head (includes the bell and neck, which are not labeled), 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 that extend down the handle for strength. Shown here are: A. Ball-peen hammer B. Straight-peen hammer C. Cross-peen hammer

thumb|upright|The claw of a carpenter's hammer is frequently used to remove nails.

A large hammer-like tool is a maul (sometimes called a "beetle"), a wood- or rubber-headed hammer is a mallet, and a hammer-like tool 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 a blow to the intended target without itself deforming. The impacting surface of the tool is usually flat or slightly rounded; the opposite end of the impacting mass may have a ball shape, as in the ball-peen hammer. Some upholstery hammers have a magnetized face, to pick up tacks. In the hatchet, the flat hammer head may be 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 (due to the presence of 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 made of aluminium or beryllium copper. In recent years, the handles have been made of durable plastic or rubber, though wood is still widely used because of its shock-absorbing qualities and repairability.

Hand-powered

  • Ball-peen hammer, or mechanic's hammer
  • Boiler scaling hammer
  • Cross-peen hammer, In modern usage, the term is mostly interchangeable with "engineer's hammer", although it can indicate a version with a slightly shorter handle.
  • Engineer's hammer, a short-handled hammer, was originally an essential components of a railroad engineer's toolkit for working on steam locomotives. Typical weight is 2–4 lbs (0.9–1.8 kg) with a 12–14-inch (30–35 cm) handle. Originally these were often cross-peen hammers, with one round face and one wedge-peen face, but in modern usage the term primarily refers to hammers with two round faces.
  • Gavel, used by judges and presiding authorities to draw attention
  • Geologist's hammer or rock pick
  • Joiner's hammer, or Warrington hammer
  • Lump hammer, or club hammer
  • Mallets, including versions made with hard rubber or rolled sheets of rawhide
  • Railway track keying hammer A titanium head has about 3% recoil energy and can result in greater efficiency and less fatigue when compared to a steel head with up to 30% recoil. Dead blow hammers use special rubber or steel shot to absorb recoil energy, rather than bouncing the hammer head after impact.

Effect of the handle

The handle of the hammer helps in several ways. It keeps the user's hands away from the point of impact. It provides a broad area that is better-suited for gripping by the hand. Most importantly, it allows the user to maximize the speed of the head on each blow. The primary constraint on additional handle length is the lack of space to swing the hammer. This is why sledgehammers, largely used in open spaces, can have handles that are much longer than a standard carpenter's hammer. The second most important constraint is more subtle. Even without considering the effects of fatigue, the longer the handle, the harder it is to guide the head of the hammer to its target at full speed.

Most designs are a compromise between practicality and energy efficiency. With too long a handle, the hammer is inefficient because it delivers force to the wrong place, off-target. With too short a handle, the hammer is inefficient because it does not deliver enough force, requiring more blows to complete a given task. Modifications have also been made with respect to the effect of the hammer on the user. Handles made of shock-absorbing materials or varying angles attempt to make it easier for the user to continue to wield this age-old device, even as nail guns and other powered drivers encroach on its traditional field of use.

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 sledgehammer) 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 traditional mechanical pile drivers, rely entirely on gravity for acceleration on the down stroke.

Ergonomics and injury risks

thumb|Hitting one's fingertip with a hammer can cause a [[bone fracture|comminuted (multi-fragment) fracture of the finger.]]

A hammer may cause significant injury if it strikes the body. Both manual and powered hammers can cause peripheral neuropathy or a variety of other ailments when used improperly. Awkward handles can cause repetitive stress injury (RSI) to hand and arm joints, and uncontrolled shock waves from repeated impacts can injure nerves and the skeleton. Additionally, striking metal objects with a hammer may produce small metallic projectiles which can become lodged in the eye. It is therefore recommended to wear safety glasses.

War hammers

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

Symbolism

thumb|upright|A T-shaped hammer in the upper left corner of the coat of arms of [[Tampere]]

The hammer, being one of the most used tools by man, has been used very much in symbols such as flags and heraldry. In the Middle Ages, it was used often in blacksmith guild logos, as well as in many family symbols. The hammer and pick are used as a symbol of mining.

In mythology, the gods Thor (Norse) and Sucellus (Celtic and Gallo-Roman), and the hero Hercules (Greek), all had hammers that appear in their lore and carried different meanings. 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.

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

A political party in Singapore, Workers' Party of Singapore, based their logo on a hammer to symbolize the party's civic nationalism and social democracy ideology.

A variant, well-known symbol with a hammer in it is the hammer and sickle, which was the symbol of the former Soviet Union and is strongly linked to communism and early socialism. The hammer in this symbol represents the industrial working class (and the sickle represents the agricultural working class). The hammer is used in some coats of arms in former socialist countries like East Germany. Similarly, the Hammer and Sword symbolizes Strasserism, a strand of Nazism seeking to appeal to the working class. Another variant of the symbol was used for the North Korean party, Workers' Party of Korea, incorporated with an ink brush on the middle, which symbolizes both Juche and Songun ideologies.

In Pink Floyd – The Wall, two hammers crossed are used as a symbol for the fascist takeover of the concert during "In the Flesh". This also has the meaning of the hammer beating down any "nails" that stick out.

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.

Judah Maccabee was nicknamed "The Hammer", possibly in recognition of his ferocity in battle. The name "Maccabee" may derive from the Aramaic maqqaba. (see .)

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 civil rights movement.

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<gallery class="center">

File:Buck Knives Hammer (5075278861).jpg|Ball-peen hammer

File:Stockhammer.JPG|Bush hammer

File:Hammer2.jpg|Claw hammer

File:Hammer-1.jpg|Cross-peen hammer

File:Hammer dog-head.jpg|Dog-head hammer (blacksmithing)

File:Framing hammer.jpg|Framing hammer

File:BrokenConcretion22.jpg|Geologist's hammer

File:Hifit-hammer.jpg|HiFIT-hammer for aftertreatment of weld transitions

File:Hammer Long cross-face.jpg|Long cross-face hammer (blacksmithing)

File:Sledgehammer.jpg|Post maul

File:Climbing Hammer.png|Rock climbing hammer

File:Gummihammer.png|Rubber mallet

File:Sledgehammers-1.jpg|Sledgehammers

File:Hammer straight pane sledge.jpg|Straight pane sledgehammer

File:Hammer twist.jpg|Twist hammer (blacksmithing)

File:Hammer tapissier.jpg|Upholstery hammer

File:Mallet menuisier.jpg|Wooden mallet

</gallery>

See also

  • Hammer Museum (Haines, Alaska)
  • Mjölnir

References

  • Types of Hammers (images and descriptions)
  • "Choosing a Hammer". Popular Science, June 1960, pp.&nbsp;164–167.