The helical gear is by plastic and the worm screw is by steel.

 

The goal of this project was a strong noise reduction, ensuring mechanical strength and durability. To achieve this goal it has been chosen a toothing profile with different circular thickness between pinion and gear, so as to have the contact ratio as large as possible, consistent with the size of two gears.

 

Plastic bevel gears for professional power tools
In this case the project goal was a strong noise reduction, ensuring mechanical strength and durability, obtained by the increase of contact ratio.