Different Types of Gears and Their Applications

Gears are defined as toothed wheels or multilobed cams, which transmit power and motion from one shaft to another by means of successive engagement of teeth.

Gears can also be defined as toothed cylindrical components which meshes with another toothed cylindrical component to transmit power and motion from one shaft to another.

In other words, we can say that Gears are transmission components that transmit power from one point to another.

Gears are broadly classified into four groups i.e.

• Spur Gear
• Helical Gear
• Bevel Gear
• Worm Gear

Now let’s discuss different types of gears and applications

Spur Gear

A pair of spur gear is shown in fig.

Spur Gear pair

In the case of spur gears, the teeth are cut parallel to the axis of the shaft. As the teeth are parallel to the axis of the shaft, spur gears are used only when the shafts are parallel.

The profile of the gear tooth is in the shape of an involute curve and it remains identical along the entire width of the gear wheel. Spur gears impose radial load on the shafts.

Advantages of Spur Gear

• Spur gears have high transmission capacity with high efficiency.
• Spur gears are easy to install.
• Spur gears are highly reliable.

Disadvantages of Spur Gear

• Costly as compared to belt drives.
• Limited center distance.
• When operating at higher speeds they produce higher noise.

Applications of Spur Gear

• Metal cutting machines.
• Power plants.
• Mechanical clocks and watches.
• Fuel pumps.

Spur Gear Materials

• Cast iron
• Alloy steel
• Cast steel
• Carbon steel
• Copper
• Brass
• Plastic
• Aluminum

Also see Spur Gear materials, applications, and advantages.

Helical Gear

A pair of helical gears is shown in fig.

Helical Gear Pair

The teeth of helical gears are cut at an angle with the axis of the shaft.

Helical gears have an involute profile similar to that of spur gears. However, this involute profile is in a plane, which is perpendicular to the tooth element.

The magnitude of the helix angle of pinion and gear is the same; however, the hand of the helix is opposite.

A right-hand pinion meshes with a left-hand gear and vice versa. Helical gears impose radial and thrust loads on the shafts.

Advantages of Helical gear

• Quiet and smooth operation
• Helical gears can be mounted on parallel and crossed sections.

Disadvantages of Helical gear

• Power loss due to slippage is more.
• Less efficient than spur gears.

Applications of Helical gear

• They are used in automobiles.
• Gearboxes
• Aerospace industries.
• Textile industries.

Helical gear Material

Depending upon the application, materials used for helical gear are

• Steel
• Stainless steel
• Cast iron
• Brass

Herringbone or Double Helical Gear

Herringbone gear

There is a special type of helical gear, consisting of two helical gears with the opposite hand of the helix as shown in fig. It is called Herringbone gear. The construction results in equal and opposite thrust reactions, balancing each other and imposing no thrust load on the shaft. Herringbone gears are used only for parallel shafts.

Bevel Gear

Bevel gears, as shown in fig. have the shape of a truncated cone. The size of the gear tooth, including the thickness and height, decreases towards the apex of the cone.

Bevel gears are normally used for the shafts, which are right angles to each other. This, however, is not a rigid condition and the angle can be slightly more than 90 degrees.

The tooth of the bevel gears can be cut straight or spiral. Bevel gears impose radial and thrust loads on the shafts.

The worm gear as shown in fig. consists of a worm and a worm wheel.

The worm is in the form of a threaded screw, which meshes with the matching wheel.

The threads on the worm can be single or multi-start and usually have a small lead.

Worm gear drives are used for shafts, the axes of which do not intersect and are perpendicular to each other. The worm imposes a high thrust load, while the worm wheek imposes a high radial load on the shafts.

Worm gear drives are characterized by a high-speed reduction ratio.