SCISSORS

cutting instrument consisting of a pair of opposed metal blades that meet and cut when the handles at their ends are brought together. The term shears sometimes denotes large-size scissors. Modern instruments are of two types: the more usual pivoted blades have a rivet or screw connection between the cutting ends and the handle ends; spring shears have a C-shaped spring connection at the handle ends. Spring-type scissors probably date from the Bronze Age and were commonly used in Europe until the end of the Middle Ages. Pivoted scissors of bronze and iron were used in ancient Rome and in China, Japan, and Korea. In Europe their domestic use dates from the 16th century, but not until 1761, when Robert Hinchliffe of Sheffield, Eng., first used cast steel in their manufacture, did large-scale production begin. In the 19th century much hand-forged work was produced, with elaborately ornamented handles. By the end of the 19th century, styles were simplified for mechanical-production methods. The two blades are made to twist or curve slightly toward one another so that they touch in only two places: at the pivot, or joint, and at the spot along the blades where the cutting is taking place. When completely closed, the points of the blades touch. In the case of the finest cutting instruments, the two unfinished metal blanks and the fasteners are coded with an identifying mark so they can be manufactured as a set. Blanks are usually made from red-hot steel bars that are forged at high speed between the dies of drop hammers, but others also of satisfactory quality may be made from cold-forged blanks. The steel may contain from 0.55 to 1.03 percent carbon, the higher carbon content providing a harder cutting steel for certain applications. Stainless steel is used for surgical scissors. Certain nonferrous alloys that will not produce sparks or interfere with magnetism are employed in making scissors for cutting cordite and magnetic tape. Handle and blade are usually constructed in one piece, but in some cases the handles are electrically welded to the steel blades. Expert sharpening is required to restore the edge-angle sharpness; each blade is passed smoothly and lightly across a grinding wheel, following the twist of the blade, with an even pressure throughout the stroke to avoid causing ridges or other irregularities. A special form of shears used for sheet-metal work, called tin shears, or tin snips, is equipped with high-leverage handles to facilitate cutting the metal. Another special form, pruning shears, are designed for trimming shrubs and trees.