Worm Gear Reducer Efficiency and Reduction RatioSeveral factors influence the overall efficiency of a worm gear reducer. The Dudley Gear Handbook provides formulas to compare and estimate worm gear efficiencies. The lead angle of typical worm gear geometry usually varies between 2 and 40 deg. Typical worm gear reducers use a hardened steel worm driving a bronze worm gear. The efficiency of a new worm gear reducer is often less than a well-run-in reducer due in part to the fact that the gear teeth on a new worm gear are not smooth.