In the power transmission industry, we're always hearing about the new developments in chain products, solutions to problems on chain wear, etc. However, there is another side to power transmission that is commonly overlooked by many PT equipment users - the sprocket. The sprocket seems to be the last item ordered, or even replaced, when the chain wears out or when the system needs to be serviced.

One likely reason may be that it's considered a commodity item.

All it does is connect the chain to the shaft - however; there really is more to sprockets than meets the eye.

What is a sprocket?

- In the power transmission industry, the sprocket transmits power from one source to another - the first source being the motor drive, the second, the receiving source - the chain.

There are three basic types of sprockets used in PT drive applications: Drive Sprocket -This sprocket is considered the 'power source' sprocket.

It transmits the power toward the particular application.

Driven Sprocket -This sprocket is driven by the drive sprocket and turns the shaft for the application (such as a conveyor).

Idler Sprocket -This third type of sprocket is used to take up tension on the slack side of the chain.

It is not considered part of the powering system.

It typically rides on a shaft with bearings.

Sprocket materials - most standard sprockets are manufactured from steel.

They can be made from many type of material, but the offerings from most manufacturers are based upon their own equipment limitations and the tooling available to cut the teeth.

Below is a listing of typical sprocket materials and their most frequent application environments.

Steel - Is considered the most typical construction material.

It is available in different hardness levels (covered later) and is used in all types of applications.

Bronze - Is a metal used in non-magnetic applications where 'no sparking' is required.

It can also withstand the abuse of some corrosive environments.

Brass - Is also a non-magnetic application material with the ability to stand up in a number of corrosive environments.

Stainless Steel - This is the most common material used for corrosive environments.

It is widely applied throughout in the food processing industry and most manufacturers have types approved for direct food contact.

Titanium - Light weight and very strong, this metal is a silvery, dark grey colour and is designed for highly corrosive applications or direct chemical exposure such as in the electrical industry where printed circuit boards are cleaned.

Aluminium - Silvery, light weight metal that can resist corrosion but is restricted to light duty, light load applications.

Typically used in belt and pulley applications (timing belts).

Nylon (Plastic) - As with roller chain, nylon is also used for anti-corrosive environments, as well as for quietness.

Nylon materials are also generally less expensive than metal.

Nylon sprockets can be used in the food industry, as they hold up well in wash down situations.

These plastic sprockets can be constructed from electro-conductive through heat resistant styles - similarly found in plastic chain.

Selecting a sprocket style - two of the most difficult areas to understand for individuals learning about sprockets are how to make a selection from the wide variety available and which size is required.

Fundamentals of sprockets- A Sprocket Primer - there is no single answer.

It is important to analyse the whole power transmission application when selecting the sprocket.