1. Straight face worm gear
2. Hobbed straight face worm gear
3. Concave face worm gear Straight Face Worm Gear Straight face worm gear is similar to a helical gear in which straight teeth are cut by a form cutter. Aas it has only point contact by worm thread, thus it is use for light service. Hobbed Straight Face Worm Gear Hobbed straight face worm gear is too use for light service but its teeth are cut by a hob, after which the outer surface is twisted. Concave Face Worm Gear Concave face worm gear is usual standard type and is use for every heavy service and general industrial uses. Teeth of this gear are cut by a hob of same pitch diameter as mating worm to raise contact area.