Best choice of gearing when high drive reduction is Worm wheel gear required. Worm 
Wheels resemble spur gears with the addition of a throat cut in to the O.D. of wheel. The throat permits the worm wheel to totally envelope the threads of the worm. Threads, not tooth are cut on the worm, and by adjusting the amount of threads, different ratios can be achieved without altering mounting plans. A unique feature of Worm and Wheel assemblies can be their ability to prohibit back driving
Pitch: 16 to 64 DP and 1.5 to .5 MOD
Material: Brass for Worm Gear and Stainless Steel for Worm
Single, Double or Quad Start