One distinguishes two types of cylindrical worm and wormwheel：
A set “worm and helical gear”
A set “worm and wormwheel”
The first set is a special case of the ‘helical gears for crossed shafts’ where the pinion for only counts l, 2, 3 (or a small number of) teeth and is characterised by a large helix angle of the tooth.
The calculation is the same as for the helical gears.
The choice of the module should be limited to the normalized set of normal modules. As with helical gears for crossed shafts there is only point contact between the tooth flanks so this kind of transmissions is not applicable for high loads.
For the set ‘worm and wormwheel’ the teeth of the wormwheel are being milled with a worm mill with the same basic features as the worm. In this case the gear contact is characterized by line touch, through which higher tooth forces are admissible.
When the oil immersion depth of worm bearing has reached the requirements, but the oil immersion depth of worm is not enough, oil splashing ring can be set on the worm shaft.The oil splashing ring is used to lubricate the transmission parts and bearings so as to prevent the worm bearing from being deeply immersed in oil.When the worm's PI is greater than 10m/s, the worm gear is replaced by the worm gear, which is arranged above the worm gear, known as the overhead type.Its worm gear speed is low, stirring oil loss is small, the possibility of impurities and abrasive in the oil pool into the meshing place is small.