Boston Gear® worm gears provide effective power transmission in applications requiring high ratio speed reduction in a limited space using right angle (90 deg), non-intersecting shafts. They are also the smoothest, quietest form of gearing when properly applied. Boston Gear® offers worm gears manufactured from a variety of materials, such as acetal, minlon, bronze and cast iron to suit your application's requirements. The efficiency of a worm gear drive depends on the lead angle and number of starts on the worm, the ratio should be kept low. To run properly, worms and worm gears operating together must have the same diametrical pitch and threads. Boston Gear® Worm Gear Without Hardened Teeth, Web, Series: D Series, 3/4 in Bore, 4.37 in Outside Dia, 25:1 Gear Ratio, 2 Number of Threads, 50 Teeth, 12 Diametral Pitch, 4.167 in, 1/2 in Face Width, Right Hand Direction of Rotation, 1.44 in Hub Dia, 0.62 in Hub Projection, 1.12 in Overall Length, 14.5 deg Pressure Angle, Bronze