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helical gear[′hel·ə·kəl ′gir]
a cylindrical gear wheel with diagonal teeth that transmits rotation between crossed shafts in a screw gear transmission. Helical gears are made from materials that have a high resistance to coupling. Such materials as steel-hardened steel, cast iron-bronze, cast iron-plastic, steel-bronze, and steel-plastic are used for helical gears operating in pairs.