Scissors & Shears

Scissors are types of tools used for cutting thin material which requires little force. more...

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.

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.

History

It is most likely that scissors were invented in 1500 BC in ancient Egypt. These were likely shears with the joint at the far end. 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".

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