The minimum number of teeth on the pinion to operate without interference in standard full height involute teeth gear mechanism with $${20^ \circ }$$ pressure angle is

Large speed reductions (greater than $$20$$) in one stage of gear train are possible through

A $$1.5$$ $$kW$$ motor is running at $$1440$$ rev/min. It is to be connected to a stirrer running at $$36$$ rev/min. the gearing arrangement suitable for this application is

To make a worm drive reversible, it is necessary to increase