... worm gears to have reductions of 20:1, and even up to 300:1 or greater. Many ... to spin it, the friction between the gear and the worm holds the worm in place. This ... differential, which is used on some high-performance cars and trucks. Material:carbon steel such as C45, 20CrMnTi, ... 40Cr, 42CrMo or stainless steel or copper or nylon and so on Process:Cutting, hobbing, lathe machining, grinding, ...