Scissors
Scissors are hand-operated cutting instruments. They consist of a pair of metal blades, or tangs, connected in such a way that the sharpened edges slide against each other. Scissors are used for cutting various thin materials, such as paper, cardboard, metal foil, thin plastic, cloth, rope and wire. Scissors can also be used to cut hair and food.
Scissors and shears exist in a wide variety of forms depending on their intended uses. Children's scissors, used only on paper, have dull blades and rounded corners to ensure safety. Scissors used to cut hair or fabric must be much sharper. The largest shears used to cut metal or to trim shrubs must have very strong, sharp blades.
Specialized scissors include sewing scissors, which often have one sharp point and one blunt point for intricate cutting of fabric, and nail scissors, which have curved blades for cutting fingernails and toenails.
Special kinds of shears include pinking shears, which have notched blades that cut cloth to give it a wavy edge, and thinning shears, which have teeth that cut every second hair strand, rather than every strand giving the illusion of thinner hair.
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Terminology
The noun "scissors" is treated as a plural noun, and therefore takes a plural verb ("these scissors are"). Alternatively, this tool is also referred to as "a pair of scissors", in which case it (a pair) is singular and therefore takes a singular verb ("this pair of scissors is"). In theory each of the two blades of the tool is a "scissor" in its own right, although in practice such usage is seldom heard.
The word shears is used to describe similar instruments that are larger in size. As a general rule:
- scissors have blades less than 6 in (15 cm) long and usually have handles with finger holes of the same size.
- shears have blades longer than 6 in (15 cm) and often have one small handle with a hole that fits the thumb and one large handle with a hole that will fit two or more fingers.
History
It is most likely that scissors were invented in 1500 BC in ancient Egypt.[1] The earliest known scissors appeared in Mesopotamia 3,000 or 4,000 years ago. These were of the 'spring scissor' type comprising two bronze blades connected at the handles by a thin, curved strip of bronze. This strip served to bring the blades together when squeezed and to pull them apart when released.
Cross-bladed scissors were invented by the Romans around AD 100.
Pivoted scissors of bronze or iron, in which the blades were connected at a point between the tips and the handles, were used in ancient Rome, China, Japan, and Korea. Spring scissors continued to be used in Europe until the sixteenth century and the idea is still used in almost all modern scissors.
Early manufacture
During the Middle Ages and Renaissance, spring scissors were made by heating a bar of iron or steel, then flattening and shaping its ends into blades on an anvil. The centre of the bar was heated, bent to form the spring, then cooled and reheated to make it flexible.
Pivoted scissors were not manufactured in large numbers until 1761, when Robert Hinchliffe produced the first pair of modern-day scissors made of hardened and polished cast steel. He lived in Cheney Square, London and was reputed to be the first person who put out a signboard proclaiming himself "fine scissor manufacturer".[2]
During the nineteenth century, scissors were hand-forged with elaborately decorated handles. They were made by hammering steel on indented surfaces known as bosses to form the blades. The rings in the handles, known as bows, were made by punching a hole in the steel and enlarging it with the pointed end of an anvil.
In 1649, in a part of Sweden that is now in Finland, an ironworks was founded in the "Fiskars" hamlet between Helsinki and Turku. In 1830, a new owner started the first cutlery works in Finland, making, among other items, scissors with the Fiskars trademark. In 1967, Fiskars Corporation introduced new methods to scissors manufacturing.[3]
Description and operation
A pair of scissors consists of two pivoted blades. The cutting edges of most scissors are not particularly sharp; it is primarily the shearing action between the two blades that cuts the material. Children's scissors are even less sharp, and the tips of the blades are blunt for safety.
Mechanically, scissors are a first-class double-lever with the pivot acting as the fulcrum. For cutting thick or heavy material, the mechanical advantage of a lever can be exploited by placing the material to be cut as close to the fulcrum as possible. For example, if the applied force (i.e., the hand) is twice as far away from the fulcrum as the cutting location (e.g., piece of paper), the force at the cutting location is twice that of the applied force at the handles. Scissors cut material by applying a local shear stress at the cutting location which exceeds the material's shear strength.
Specialized scissors, such as bolt cutters, exploit leverage by having a long handle but placing the material to be cut close to the fulcrum.
For disabled people without the use of their hands, there are specially designed foot operated scissors; for paraplegics there is also a motorized mouth-operated style of scissor.
Kitchen scissors
Kitchen scissors, also known as kitchen shears, are similar to common scissors. The main difference is the location of the fulcrum. Kitchen scissors have the fulcrum located farther from the handles to provide more leverage and thus more cutting power. High quality kitchen scissors can easily cut through the breastbone of a chicken and other forms of meat embedded with hard dense bones.
'Handed' scissors
Most scissors are best-suited for use with the right hand, but left-handed scissors are designed for use with the left hand. Because scissors have overlapping blades, they are not symmetric. This asymmetry is true regardless of the orientation and shape of the handles: the blade that is on top always forms the same diagonal regardless of orientation. Human hands are also asymmetric, and when closing, the thumb and fingers do not close vertically, but have a lateral component to the motion. Specifically, the thumb pushes out and fingers pull inwards. For right-handed scissors held in the right hand, the thumb blade is further from the body so that the natural tendency of the right hand is to force the cutting blades together. Conversely, if right-handed scissors are held in the left hand, the natural tendency of the left hand would be to force the cutting blades laterally apart. Furthermore, with right-handed scissors held by the right-hand, the shearing edge is visible, but when used with the left hand the cutting edge of the scissors is behind the top blade, and one cannot see what is being cut.
Some scissors are marketed as ambidextrous. These have symmetric handles so there is no distinction between the thumb and finger handles, and have very strong pivots so that the blades simply rotate and do not have any lateral give. However, most "ambidextrous" scissors are in fact still right-handed. Even if they successfully cut, the blade orientation will block the view of the cutting line for a left-handed person. True ambidextrous scissors are possible if the blades are double-edged and one handle is swung all the way around (to almost 360 degrees) so that the back of the blades become the new cutting edges. Patents (U.S. Patent 3,978,584) have been awarded for true ambidextrous scissors.
Shears
Although often used interchangeably with "scissors", the term shears is reserved by those in the industry for scissors longer than 15 cm (5.9 in).[4] Others assert that scissors are symmetric whereas shears distinguish between the thumb hole and the finger hole.[5] Like scissors, shears combine slightly offset jaws to cut material through physical shear, and combine this with levers to apply a considerable small force. Shears are usually intended for cutting much heavier material than scissors.
Specialised scissors
There are several specialised scissors and shears used for different purposes. Some of these are:
- Sewing Chatelaine Scissors. Chatelaine is a French term meaning "mistress of a castle, chateau or stately home", and dates back to the middle ages. It refers to an ornamental clasp or hook from which chains were hung from the waist, holding perhaps, a purse, watch, keys, scissors or thimble case. The sewing chatelaine became a popular ornamental appendage worn by Victorian ladies at their waist, but disappeared when fashion changed and skirts were no longer full and long. Sewing chatelaines are now produced and worn as pendants around the neck.
- Pinking shears are scissors with a serrated cutting edge for cutting cloth so that the fabric does not fray.
- Tin snips are scissors for cutting through sheet metal like tin plate, or galvanised iron.
- Pruning shears (secateurs) and loppers are gardening scissors for cutting through branches of trees and shrubs.
- Trauma shears, or "tuff cuts", are robust scissors used in emergency medical response and rescue.
- Thinning scissors are used for thinning thick hair to avoid a bushy look
- Grass and hedge shears are used for trimming grass and hedges.
- Jaws of Life (see Hydraulic rescue tools) for cutting heavy sheet metal in a rescue response.
- Throatless shears are used for cutting complex shapes in sheet metal.
- Wool shears are used for collecting wool from an animal's fleece.
- Poultry shears are to cut poultry.
- Hair shears – for cutting hair as a cosmetologist or hairdresser, or for dog grooming.
See also
- Bolt cutters cut through heavy wire and bolts.
- Hemostat resembles a pair of scissors, but is used as a clamp in surgery and does not cut at all.
- Nippers cut small pieces out of tile.
- Pliers used for holding and crimping metal or wire.
References
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