Scissors
From Wikipedia, the free encyclopedia
Scissors are types of tools used for cutting thin material which requires little force.
They are used for cutting, for example: paper, cardboard, metal foil, thin plastic, food, cloth, rope, and wire. Scissors can also be used to cut hair. Unlike a knife, a pair of scissors consists of two pivoted blades, each called a scissor. Most types of scissors are not particularly sharp; it is primarily the shearing between the two blades which cuts. Children's scissors are even less sharp, and the blades are often protected with plastic.
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[edit] Mechanics
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. Specialized scissors, like bolt cutters exploit leverage by having a long handle but placing the material to be cut close to the fulcrum. Scissors cut material by applying a local shear stress at the cutting location which exceeds the material's shear strength.
[edit] History
It is most likely that scissors were invented in 1500 BC in ancient Egypt.[1] These were likely shears with the joint at the far end.[2] Cross-bladed scissors were invented by Romans around AD 100.
An immense stride in perfecting scissors was taken in 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".[3]
In a part of Sweden (now in Finland) an ironworks was started 1649 in the hamlet "Fiskars" between Helsinki and Turku. In 1830 a new owner started the first cutlery works in Finland, making among others scissors with the trade mark Fiskars. Fiskars Corporation introduced new methods in the manufacturing of scissors in 1967.[4]
[edit] 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.[citation needed]
[edit] Left handed scissors
Most scissors are best suited to use with the right hand, but left-handed scissors are designed for use by the left. Left-handed scissors have handles which are comfortable to hold in the left hand. Because scissors have overlapping blades, they are not symmetric. This asymmetry is true regardless of the orientation and the 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 closer to 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. They have symmetric handles so there is no distinction between the thumb and finger handles, and they 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[1]. Patents (U.S. Patent 3,978,584) have been awarded for true ambidextrous scissors.
Using scissors designed for the wrong hand is difficult for most people, even for left-handers who have become accustomed to using the more readily available right-handed scissors. They have to unnaturally force the blades together to cut and stretch their necks over the top blade to see what is being cut. This unnatural motion can also cause marks on the hand, sores, and eventually calluses.
[edit] Shears
Although often used interchangeably with "scissors," the term shears is reserved by those in the industry for scissors longer than 15 cm.[5] Others assert scissors are symmetric whereas shears distinguish between the thumb hole and the finger hole.[6] Like scissors, shears combine slightly offset jaws to cut material through physical shear, and combine this with levers to apply a considerable shear force. Shears are usually intended for cutting much heavier material than scissors.
[edit] Specialized scissors
There are several specialized scissors and shears used for different purposes. Some of these are:
- 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 corrugated galvanised iron.
- Pruning shears (secateurs) and loppers are gardening scissors for cutting through branches of tree and shrubs.
- Trauma shears, or "tuff cuts", are robust scissors used in emergency medical response and rescue.
- Trimming scissors are used for thinning thick hair to avoid a bushy look
- Grass shears are used for trimming grass.
- 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 pet grooming.
In the following, the blades meet and compress the material instead of shearing it so they are technically not scissors:
- Bolt cutters cut through heavy wire and bolts.
- Nippers cut small pieces out of tile.
- Hemostat resembles a pair of scissors but has a locking clamp instead of a blade; it is used in surgery and does not cut at all.
- Pliers used for holding and crimping metal or wire.
[edit] Notes
- ^ Who Invented Scissors
- ^ scissors@Everything2.com
- ^ http://freepages.history.rootsweb.com/~exy1/fh_material/18C_sheffield/ch4.txt
- ^ http://www.fiskars.fi/pdf/Fiskars_history_eng.pdf
- ^ Arius Eickert Differences Between A Scissor And Shear Technical Article
- ^ http://www.canadacutlery.com/product/facts_on_scissors.pdf
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