Pliers in the general sense are an ancient and simple invention, no singular point in history or singular inventor can be credited. Early metal working processes from several millennia BC would have required plier-like devices to handle hot materials in the process of smithing or casting. Development from wooden to bronze pliers would have probably happened sometime prior to 3000 BC . Among the oldest illustrations of pliers are those showing the Greek god Hephaestus in his smithy. Today, pliers intended principally to be used for safely handling hot objects are usually called tongs. The number of different designs of pliers grew with the invention of the different objects which they were used to handle: horse shoes, fasteners, wire, pipes, electrical and electronic components.
The basic design of pliers has changed little since their origins, with the pair of handles, the pivot (often formed by a rivet), and the head section with the gripping jaws or cutting edges forming the three elements. In distinction to a pair of scissors or shears, the plier's jaws always meet each other at one pivot angle.
Pliers are an instrument that convert a power grip—the curling of the fingers into the palm of the hand—into a precision grip, directing the power of the hand's grip in a precise fashion on to the objects to be gripped. The handles are long relative to the shorter nose of the pliers. The two arms thus act as first class levers with a mechanical advantage, increasing the force applied by the hand's grip and concentrating it on the work piece.
The materials used to make pliers consist mainly of steel alloys with additives such as vanadium or chromium, to improve alloy strength and prevent corrosion. Often pliers have insulated grips to ensure better handling and prevent electrical conductivity. In some lines of fine work (such as jewellery or musical instrument repair), some specialised pliers feature a layer of comparatively soft metal (such as brass) over the two plates of the head of the pliers to reduce pressure placed on some fine tools or materials. Making entire pliers out of softer metals would be impractical, reducing the strength required to break or bend them.
- Combination pliers or lineman's pliers
- Flat-nose pliers, also known as "duckbill," after their resemblance to a duck's bill. With long, narrow, flat jaws, they are stronger than long-nose (needle-nose) pliers, but less able to reach into really confined spaces
- Round-nose pliers, sometimes called snub-nosed pliers
- Long-nose pliers, needle-nose pliers, or snipe-nose pliers, which have long, narrow jaws for gripping in confined spaces
- Locking pliers, also called "vise grips" or "mole grips"
- Tongue and groove pliers, also called Channellock pliers after a common manufacturer.
- Parallel pliers, which have jaws (usually smooth) which come together in a completely parallel motion, as opposed to regular pliers which rotate until contact. This design is intended to increase the surface area on materials the pliers are used on, decreasing pressure and potential for causing indentations.
Special purpose pliers
- Wire-stripping pliers - cuts and removes insulation on electrical wire while leaving the wire intact
- Fencing tools - pliers that include a hammer, wire cutter and nail puller on one tool
- Retaining-ring or circlip pliers, which are used for fixing or loosening retaining rings
- Nail-pulling pliers - an adaptation of the end nipper used for cutting wire; the jaws may be asymmetric, allowing the nail to be pulled out with a rocking motion on the surface in which it is imbedded.
- Glass-breaking/grozz pliers (breaker-grozier pliers).
- Slip joint pliers, which are similar to combination pliers but whose pivot can be slipped between two holes when the jaws are fully open to change their size
- Groove-joint or tongue-and-groove pliers, occasionally called water-pump pliers, also referred to by the name of a well-known manufacturer, such as Channellock, with adjustable jaw sizes, that are designed to grip various sizes of round, hexagon, flat or similarly shaped objects
- Combination pliers or lineman's pliers
- Diagonal pliers (wire cutters, side-cutting pliers or side cutters) not really pliers as only used for cutting
- Pinching pliers (end-nippers)
- Needle-nose pliers - designed for gripping, but typically incorporate a cutter for 'one-tool' convenience.
- For crimping electrical terminals and connectors (solderless connections)
- For crimping metal rings or tags on livestock
- For crimping metal security seals on cargo carriers
- For crimping an impression on a document - as in a notary's seal
- For crimping laboratory vials
- For crimping bottles with sprayer tops, such as perfume bottles
- developed by NASA engineers to enable an astronaut to turn a nut in zero gravity. The clamping motion of the hand is converted to rotational motion to drive a socket wrench
- Bellis, Mary. 'The History of Hardware Tools'. http://inventors.about.com/library/inventors/blpliers.htm Accessed 12/16/2008.