Description and operation

Description and operation

A pair of scissors consists of two pivoted blades. In lower quality scissors the cutting edges are not particularly sharp; it is primarily the shearing action between the two blades that cuts the material. In high quality scissors the blades can be both extremely sharp, and tension sprung - to increase the cutting and shearing tension only at the exact point where the blades meet. The hand movement (pushing with the thumb, pulling with the fingers in right handed use) can add to this tension. An ideal example is in high quality tailors scissors or shears, which need to be able perfectly cut (and not simply tear apart) delicate cloths such as chiffon and silk.

Children's scissors are usually not particularly sharp, and the tips of the blades are often blunted or 'rounded' 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 people who do not have the use of their hands, there are specially designed foot operated scissors. Some quadriplegics can use a motorized mouth-operated style of scissor