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small slender instruments widely used in sewing and knitting, medicine, printing, and other industries. There are needles for machine and hand sewing. Machine needles are usually cylindrical in form with a conical point; sometimes they have special points to cut openings in various shapes, including oval, rhomboid, triangular, and square (for leather, oilskin, and impregnated fabrics). Needles may be straight or bent. Some needles have a hook at the sharp end instead of an eye. They are manufactured in various sizes (0.25– 4.0 mm in diameter) and numbered accordingly: the numbering is based on needle diameter and expressed in hundredths of a millimeter (no. 60 is 0.60 mm in diameter, no. 120 is 1.20 mm). Hand needles are classified by number according to length and diameter—for example, no. 1 to no. 9 needles range in thickness from 0.6 to 1.0 mm and in length from 30 to 50 mm.
An engraving needle is a fine steel rod (like an ordinary sewing needle, but with a point shaped like a cone, a truncated cylinder, or a blade) set into a wooden handle. It is a basic tool in etching, drypoint engraving, and engraving on cardboard, and it is an auxiliary tool in lithography and mezzotinting.
the needlelike or scaly leaves of many coniferous trees and shrubs. Needles are well adapted to the unfavorable conditions of hot summers and cold winters. They are usually perennial, falling from the tree gradually. The epidermis has a thick cuticle; the stomata are submerged. The pulp consists of parenchymal cells with chlorophyll granules; in pines the cell walls form intracellular outgrowths and folds that increase the photosynthesizing surface of the leaf. In the center of each needle are one or two conducting bundles. The needles of many species contain resin canals. The needles discharge into the atmosphere special substances called phytoncides, which influence the composition of the atmospheric microflora. Fallen needles form a slowly decomposing forest floor. The needles of certain trees are used to obtain fir and other oils, vitamins, meal (pine, spruce), and plant fiber.