If you use equipment with casters, you have likely experienced caster malfunctions at some point. The great news is that casters are easy to replace by yourself if you have some general knowledge about their anatomy and function, as well as which type of caster you need for your specific "vehicle" or equipment. 

Casters are the part of carts, materials handling equipment, office chairs, etc. that help these objects to move. The principal caster wheel parts include a wheel, framing components, and pieces that attach to your vehicle. Though it may seem like when a caster breaks, the vehicle is no longer functional, you can easily perform a DIY caster replacement to save money on an entirely new piece of equipment. 

Today, the experts at Caster Central present the following guide on caster anatomy to inform you of the functions of different types of casters and how to address a problem when a caster breaks.

Why the Anatomy of a Caster Is Important

Understanding the anatomy of casters is important as you determine the problem with a malfunctioning caster and, thus, fix it. Different models also have unique caster wheel parts, meaning their principal function is different. Understanding the basic anatomy of the four types of casters will allow you to choose the correct replacement model if you need an entirely new rig. 

Basic Caster Anatomy

All casters include a wheel. In some casters, this wheel only moves in a straight line and cannot rotate in multiple directions. In swivel models, this wheel can rotate 360 degrees, allowing the vehicle to roll in multiple directions. 

Casters also include a fork, which is the inverted U-shaped bracket that attaches the wheel to the mounting component. In stem casters, the fork and mounting component are one part, as the fork attaches directly to the stem (which is the mounting component). The fork's bracket directly attaches to the wheel's axle on either side.  

To mount/attach the caster to your vehicle, the rig includes either a top plate or a stem. A top plate is a piece of square metal that bolts directly to the vehicle and stabilizes the caster. Top plate casters are commonly used for industrial equipment due to their high weight capacity, but they are useful for smaller vehicles as well. 

On the other hand, stem casters directly attach to your vehicle using either a screw head or a simple cylinder that you must bolt to the equipment. When choosing the correct stem caster, taking diameter, length, and attachment methods into account is imperative to get the correct model for your vehicle. 

Caster Wheel Anatomy

Caster wheels use the following components:

• Tread: The tread is the part of the wheel that touches the ground. The tread either molds onto a hub or makes up the entirety of the wheel. 
• Hub: The hub is the inner part of the wheel that the tread attaches to. Frequently, the composition of the hub is a metal such as steel or cast iron. Other hubs have a nylon composition.
• Axle: The axle is the bar that goes through the center of the hub or tread. This bar attaches to the two holes in the fork's bottom U-bracket, allowing the wheel to spin.
• Brakes: Caster brakes are not always part of the rig. However, when factories have included brakes, they work by stopping the axle or tread from moving. In some cases, compression brakes work by stopping movement when someone applies weight (such as in office chairs). 

We will continue by breaking down the caster wheel parts of the top four rigs. 

Rigid Casters

Rigid casters are the most simplistic model, as they do not allow 360-degree movement. The fork attaches directly to the top plate, which limits the wheel to moving in a straight line only. Normally, equipment with rigid casters only uses them for the two back wheels, while the front two wheels allow swiveling movements.

Stem Caster

Stem casters are excellent materials handling solutions for objects that require frequent and easy mobility. For example, people often use stem casters for applications in the restaurant industry as they turn smoothly and can handle lighter-weight loads. Stem casters are also ideal for office chairs, sofas, and other furniture. 

Stem casters come in many varieties, such as threaded stem casters, grip ring or neck stem casters, round stem casters, and expanding adapter stem casters. Each stem has optimal usage for a particular application. Where round stems are more heavy-duty casters and therefore often used for scaffolding, grip ring casters are ideal for office chairs and light furniture due to easy installation. 

The main difference between stem caster anatomy and other rigs is the exclusion of a top plate and an exposed dust cap located above the fork. Each stem is different as well. For example, threaded stem casters have a screw-like stem, while expanding adapter stems include a hollow rubber grommet over top of the stem that expands when attached to a vehicle. 

Kingpin Caster

Kingpin casters include a kingpin rivet, top plate, ball bearing, and outer raceway. The kingpin holds the entire caster rig together, while the roller bearing allows the wheel to rotate. The main problem with kingpin casters is that if the kingpin rivet breaks, the entire rig will no longer function. 

Threaded Vs. Riveted Kingpin

When assembling a threaded kingpin caster, factories insert the threaded kingpin down through the top plate, through the center of the roller bearing, and into the top of the fork. As the name suggests, threaded kingpins have a screw-like appearance. So, to properly attach the kingpin, factories tighten a nut at the bottom of the kingpin to hold the caster rig together. 

Threaded kingpins are more expensive than riveted kingpin rigs, as riveted kingpins include a solid rivet that attaches to all the aforementioned parts with no bolt. However, riveted kingpin caster rigs are more likely to break because they include one solid part. You can tighten threaded kingpins as the components of the rig wear over time, making them more long-lasting. 

Kingpinless Caster

As the name suggests, kingpinless casters do not include a kingpin. Instead, they use an inner and an outer raceway with a ball bearing placed in the hollow part between the two raceways. The ball bearing then attaches to the fork and the top plate, allowing rotation. 

Using these caster wheel parts eliminates the chance of the kingpin breaking, meaning this rig will likely last longer than a kingpin caster. Due to the inclusion of both a top plate and a highly durable design, kingpinless casters are optimal for heavy loads and industrial applications that require both speed and 360-degree mobility. 

Looking for High-Quality Casters or Caster Hardware Online?

The professionals at Caster Central hope this guide has helped you better understand the application and utility of the casters on your equipment. Our goal is to provide you with the most economical repair solution for your casters, whether you need a new part to repair your caster rig or help choosing the correct model for your equipment. 

Caster Central provides a large selection of caster rigs and hardware replacements to ensure you can repair your casters at home and get your equipment up and running as quickly as possible. We offer both affordable and reliable caster solutions for any type of vehicle. 

If you would like to know more about caster wheel parts and rigs, check out our blog for helpful topics like caster wheel load ratings. For more information about our stock or questions about orders, contact us at 1-800-445-4082 today!