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Sprockets: The Ultimate Guide

Sprockets are crucial components of industrial drives, conveyor chain systems, vehicles, and more. Along with a belt or chain, sprockets help transfer power from one location to another. 

In this guide to sprockets, learn more about what sprockets are, what they are used for, how to tell if a sprocket is worn, and more. 

What Is a Sprocket? 

Similar to a gear, sprockets are mechanical wheels with teeth or notches. Unlike a gear, these teeth or notches are designed to rotate and engage with the links of a chain or belt rather than interacting with another gear. 

Sprockets have been used for centuries to help transfer power from one point to another. They are used in various applications, such as bicycles, vehicles, tools, and other machinery. 

What Are Sprockets Made Out of?

Sprockets are typically made out of steel, which is a hardwearing metal with a long service life. Aluminum is another popular material for its lightweight nature, which is ideal for motorbikes and bicycles. Aluminum does wear faster than steel, however. 

Sprockets can also be made out of hybrid materials like plastic and metal. Plastic teeth on sprockets typically interact with belts instead of chains. 

Characteristics and Terms of a Sprocket

There are different ways to configure a sprocket for different purposes. Sprockets have several characteristics that are important to their application:

    • Bore Size: The bore of the sprocket is the inside diameter of the hole through which the drive shaft is secured. 
    • Number of Teeth: This is the total number of teeth or notches found on the sprocket. Each of them is individually referred to as a “tooth”. 
  • Plate: The plate refers to the single plane of metal, including the teeth, but not including addons like hubs. 
    • Pitch Diameter: The pitch diameter is the diameter of the sprocket on the inner point between the teeth where the chain meets the sprocket. 
    • Outside Diameter: This is the outer diameter of the sprocket at the tips of the teeth. 
    • Caliper Diameter: The caliper diameter refers to the diameter of the sprocket’s plate without including the teeth in the measurement. If replacing sprockets with worn or broken teeth, the caliper diameter may be the only way to identify the dimensions of the original sprocket. 
    • Pitch: The pitch is the full measurement per tooth, which is usually represented in inches. The pitch is important because the distance between teeth needs to match between the pins on a chain or belt. 
  • Hub: The hub is an added thickness around the central plate of the sprocket that doesn’t include the teeth. Hubs allow sprockets to be closely fitted to the machinery that the sprocket is mounted on.
  • Strand: A strand is a set of teeth along a sprocket’s circumference. Many sprockets are single strand, though some are double, triple, or even more to grab onto multiple chains at once. They are sometimes called simplex for single strands, duplex for double strands, and triplex sprockets for triple strands of teeth. 

Types of Sprockets

There are different ways to categorize the types of sprockets. Some sprocket type definitions are determined by the sprocket’s characteristics and setup, while others define the types of sprockets based on the application of it. 

Types of Sprockets Based on Characteristics

There is a wide range of different sprocket types, which are available in a variety of shapes and sizes with varying numbers of teeth and notches. 

Here is a list of some of the broader characteristic types of sprockets:

  • Type A Sprockets: There is only a single plate with teeth. There are no hubs. 
  • Type B Sprockets: There is a hub on one side of the sprocket’s plate. 
  • Type C Sprockets: There are hubs on both sides of the plate. 
  • Type C Offset or Type D Sprockets: These also have two hubs; however, one hub has a different thickness, which makes the sprocket asymmetrical. 

Here are some more nuanced characteristic types of sprockets:

    • Double-Duty Sprockets have two teeth per pitch so that when one is worn down, the links can be moved to the next set of teeth. 
    • Hunting Tooth Sprockets have an uneven number of teeth. Hunting tooth sprockets tend to last longer than other types because the odd number of teeth means that as it turns, the links always engage a new set of teeth. 
  • Single-Pitch Sprockets have teeth that engage one tooth per chain link in a one-to-one matchup. 
  • Double-Pitch Sprockets look like a single-pitch sprocket, but the teeth only engage every other chain link. 
  • Segmental Rim Sprockets have bolt-on rims in either three, four, or more pieces. The rims can be replaced without removing the chain or shaft from the sprocket. These rims make them useful for elevators and other industrial settings because they help reduce costly shutdowns for installations and adjustments. 
  • Multiple-Strand Sprockets are used when more torque and power are needed or if the same drive shaft is powering multiple equipment pieces. 

Types of Sprockets Based on Application

These sprockets are named based on what they are designed to accomplish:

  • Idler Sprockets are not used as a drive sprocket. Instead, they are placed between the drive and driven sprocket and are used to control and maintain tension in the chain drive. Idler sprockets have built-in ball bearings, which allow them to spin freely with the drive shaft. 
  • Industrial Sprockets are made of graded stainless steel, mild steel, and cast iron, depending on the application and cost. Steel has high wear resistance and will last a long time. 
  • Drive Sprockets are located close to the motor and are powered by the shaft. They usually have a smaller diameter. 
  • Roller Chain Sprockets are the most common type of sprocket. They only work with chains, specifically chains with rolls and pins. The rollers in the chain have a gap between links that the teeth of the sprocket mesh with to turn the chain. 

Fitting a Sprocket to a Shaft

There are a number of different ways to connect a shaft to a sprocket. Two of the main ways are pilot bore sprockets and taper bush sprockets.

Pilot Bore Sprockets

These kinds of sprockets are typically used in industrial machinery, bikes, and motorcycles. Pilot bore sprockets have a cylindrical projection (a hub) that can be drilled and widened to the required size to create an excellent contact surface for the shaft. The shaft can be fixed in place with a grub screw, pin, or locking bushes. There is a limit to increasing the bore size based on the outer diameter of the hub specified by the manufacturer. 

Taper Bush Sprockets

Taper bush sprockets have a split through their bore to provide a clamp on the shaft. Then, a taper bush is used to get down to the size required to affix the shaft. 

Common Sprocket Applications

The most prominent visual that comes to mind for sprockets is on bicycles with a linked chain to transfer power from the rider’s legs to the bike’s wheels. 

Sprockets are commonly used in tracked vehicles such as tanks, farming, and construction machinery. The treads of the vehicle are the “chain” or “belt” and are pulled by the sprockets, which gives the vehicle movement. 

Sprockets are also heavily used to power roller chains, which are commonly used in industrial and commercial applications. Roller chains are used for conveyors, large industrial drives, robotics, motorized assemblies, and more. 

How to Tell If a Sprocket Is Worn

It is important to routinely check the amount of wear on sprockets in order to avoid damage to equipment. The following tips will help identify sprocket wear so you can avoid premature chain wear and unexpected shut-downs.

  • Inspect the sprocket and ensure the teeth and chain are properly engaging each other. Each chain roller should fall evenly into the trough of each tooth. 
  • Pull on the chain from the rear of the sprocket and try to pull the chain away from the teeth. If a gap can be seen between them, this indicates that the chain and sprocket are likely both worn. 
  • Check the teeth of the sprocket. Worn teeth often look sharp or are slightly hooked due to being worn by the chain. 
  • Look at the perimeter of the sprocket for indented wear patterns that resemble the chain. If you can identify the pattern on the sprocket, this is a good indicator that it needs to be replaced.

Chain Sprocket Standards and Sizes

Sprockets can have multiple strands of teeth. The most common type of sprocket is a single plate with a single row of teeth, sometimes called a simplex, which accounts for around 70 percent of market applications. Two rows of teeth are called a duplex and account for around 25 percent of applications. Finally, three strands of teeth are called a triplex, which has around five percent of market applications.

The two commonly seen standards for sprockets in North America are the American Standard (ANSI), the International Organization for Standardization (ISO), and the British Standard (BS), which is also known as the European Standard. Japan (JIN), Korea (KS), and Germany (DIN) all have chain and sprocket standards of their own, though they aren’t as prevalent in the United States. 

The sizes of sprockets are typically followed by a hyphen and 1, 2, or 3 to designate how many strands of teeth are needed for a chain. 

For example, 35-2 means size 35 with two strands of teeth for a size 35 duplex sprocket. A 16B-1 is an ISO size 16. The B means it adheres to European standards. The dash one means single strand or simplex sprocket. 

Need help getting the right sprockets? Magnum Industrial can help! We’ll help you determine the right bore, teeth, pitch, and type of sprocket to accomplish your goal! We provide quality industrial products with a supported distribution network and a dedicated team. Contact Magnum Industrial today for more information.