A dual lead worm gear is suitable for use to precision machinery and auxiliary to maintain precise revolution and equal deviation. It is precision and technology intensive gear. It is suitable for use to precision machinery and auxiliary machinery to maintain precise revolution and equal deviation. It is precision and technology intensive gear. It minimizes back-lash by creating deviation between tooth thickness of starting point andfinishing point by applying differently to A lead and B lead when it touches the tooth pitch atworm shaft. When the back-lash is increased by friction abrasion it can be corrected by wormshaft adjusted within the specified value. Repair and maintenance of its precision is lessexpensive and simplified.