Gears are a crucial part of many motors and machines. Gears assist in torque output by providing gear reduction and they adjust the path of rotation just like the shaft to the trunk wheels of automotive vehicles. Here are some simple types of gears and how they will vary from each other.
Spur gears are mounted in series on parallel shafts to achieve large gear reductions.
The most common gears are spur gears and so are found in series for large gear reductions. The teeth on spur gears are directly and are mounted in parallel on different shafts. Spur gears are found in washing machines, screwdrivers, windup alarm clocks, and other devices. These are particularly loud, spiral bevel helical gearbox because of the equipment tooth engaging and colliding. Each influence makes loud noises and causes vibration, which is why spur gears are not used in machinery like vehicles. A normal gear ratio range is 1:1 to 6:1.
Helical gears operate more smoothly and quietly in comparison to spur gears because of the way the teeth interact. The teeth on a helical equipment cut at an angle to the face of the gear. When two of one’s teeth begin to engage, the contact is gradual–beginning at one end of the tooth and maintaining get in touch with as the gear rotates into complete engagement. The typical range of the helix angle is about 15 to 30 deg. The thrust load varies directly with the magnitude of tangent of helix angle. Helical is the most commonly used equipment in transmissions. In addition they generate large amounts of thrust and use bearings to help support the thrust load. Helical gears can be utilized to adjust the rotation position by 90 deg. when mounted on perpendicular shafts. Its normal equipment ratio range is 3:2 to 10:1.
Bevel gears are used to change the direction of a shaft’s rotation. Bevel gears have tooth that are offered in directly, spiral, or hypoid shape. Straight teeth have similar characteristics to spur gears and also have a large impact when involved. Like spur gears, the normal gear 
ratio range for straight bevel gears is 3:2 to 5:1.
Spiral teeth operate exactly like helical gears. They generate less vibration and noise when compared to straight teeth. The right hands of the spiral bevel is the outer half of the tooth, inclined to visit in the clockwise path from the axial plane. The left hand of the spiral bevel travels in the counterclockwise path. The normal gear ratio range is 3:2 to 4:1.
In the hypoid gear above, the larger gear is called the crown while the small gear is called the pinion.
Hypoid gears are a kind of spiral gear where the shape can be a revolved hyperboloid rather than conical shape. The hypoid gear locations the pinion off-axis to the ring gear or crown wheel. This allows the pinion to be larger in diameter and provide more contact area.