<P> A gearbox designed using a worm and worm - wheel is considerably smaller than one made from plain spur gears , and has its drive axes at 90 ° to each other . With a single start worm , for each 360 ° turn of the worm , the worm - wheel advances only one tooth of the gear wheel . Therefore , regardless of the worm 's size ( sensible engineering limits notwithstanding ) , the gear ratio is the `` size of the worm wheel - to - 1 '' . Given a single start worm , a 20 tooth worm wheel reduces the speed by the ratio of 20 : 1 . With spur gears , a gear of 12 teeth must match with a 240 tooth gear to achieve the same 20 : 1 ratio . Therefore , if the diametrical pitch ( DP ) of each gear is the same , then , in terms of the physical size of the 240 tooth gear to that of the 20 tooth gear , the worm arrangement is considerably smaller in volume . </P>
<P> A gearbox designed using a worm and worm - wheel is considerably smaller than one made from plain spur gears , and has its drive axes at 90 ° to each other . With a single start worm , for each 360 ° turn of the worm , the worm - wheel advances only one tooth of the gear wheel . Therefore , regardless of the worm 's size ( sensible engineering limits notwithstanding ) , the gear ratio is the `` size of the worm wheel - to - 1 '' . Given a single start worm , a 20 tooth worm wheel reduces the speed by the ratio of 20 : 1 . With spur gears , a gear of 12 teeth must match with a 240 tooth gear to achieve the same 20 : 1 ratio . Therefore , if the diametrical pitch ( DP ) of each gear is the same , then , in terms of the physical size of the 240 tooth gear to that of the 20 tooth gear , the worm arrangement is considerably smaller in volume . </P>
where is a worm and wheel gear used
where is a worm and wheel gear used
gearbox
gearbox