Gears are used in tons of mechanical devices. They do several important jobs, but most significant, they provide a gear reduction in motorized equipment. This is key because, frequently, a small motor spinning extremely fast can provide more than enough power for a device, however, not enough torque. For instance, an electric screwdriver includes a very large gear reduction since it needs lots of torque to turn screws, bu­t the motor only produces a small amount of torque at a higher speed. With a gear reduction, the result speed could be reduced as the torque is increased.

One more thing gears do is change the direction of rotation. For example, in the differential between your rear tires of your car, the power is transmitted by a shaft that operates down the guts of the car, and the differential must turn that power 90 degrees to use it to the tires.

There are a lot of intricacies in the various types of gears. In this post, we’ll learn exactly how the tooth on gears work, and we’ll talk about the different type­s of gears you discover in all sorts of mechanical gadgets.­


On any gear, the ratio is determined by the distances from the guts of the apparatus to the point of contact. For example, in a Taper Lock Pulley device with two gears, if one gear is twice the size of the additional, the ratio would be 2:1.

Probably the most primitive types of gears we could look at would be a steering wheel with wooden pegs protruding of it.

The problem with this type of gear is that the length from the center of each gear to the point of contact changes as the gears rotate. This implies that the gear ratio changes as the apparatus turns, and therefore the output velocity also changes. If you used a gear like this in your car, it could be impossible to maintain a continuous speed — you would be accelerating and decelerating continuously.

Many contemporary gears use a special tooth profile named an involute. This profile gets the very important real estate of maintaining a constant speed ratio between the two gears. Just like the peg wheel above, the contact stage moves; but the shape of the involute gear tooth compensates for this movement. Find this section for information.

Now let’s check out some of the various types of gears.