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Comparing Plain and Finished Bore

Aluminum pulley with bore with timing belt

  

Introduction to Bore Types

Boring is a specific type of cutting process that uses a tool, sometimes referred to as a boring head, to enlarge an existing hole in a particular component. Note that this isn't the same process as traditional drilling, which is used to create an initial hole.

Consider all this within the context of a sprocket. Sprockets are essentially wheels - they have teeth that lock onto a chain, usually as part of a pulley and gear system. The teeth of the sprocket latch onto the chain and the force created moves other parts in the system. The straightforward, rotational movement is what the entire system functions around.

That sprocket is attached to a shaft via a hole in the center - in this case, a bore. Different bore types are needed depending on properties like the chain size, the tooth count, and others.

All told, there are two distinct bore types to choose from depending on your needs. Understanding the properties of each one, not to mention the advantages and disadvantages, is the key to making the most informed decision possible.

What is a Plain Bore?

Characteristics

Any component that has a plain bore will have what is referred to as an untapered bore drilled through the center.

As you would expect from something called a "plain" bore, this is a simple, cost-effective solution. Plain bores are made from materials that are resistant to potential issues like corrosion and, barring extreme situations, are generally maintenance-free.  They’re commonly used for repair or prototype applications.  Plain bore parts often require further bore modification to make them usable in the desired application. 

Applications & Benefits

The types of components that include plain bores are usually things like sheaves, sprockets, gears, and pulleys. The major benefit you get from this is one of variety - there are simply more options available in terms of how to mount a particular component to a shaft.

Plain Bore to Finished Bore

A plain bore can be opened as needed to increase the diameter of the bore itself. This means that you can start with a plain bore and then later transition into a finished bore should the situation call for it. That bore can also be fitted to include screws, pins, and anything else that you need.

What is a Finished Bore?

Characteristics

When a component has a finished bore, it is essentially a plain bore that has either set screws or a keyway added to it. Sometimes, both are necessary - it really does come down to the application.

Set screws, as the name implies, are used to secure a component to a shaft. This helps prevent slipping. They're regularly used in situations where you're working with a smaller piece of machinery, or when you need to move light loads during manufacturing.

Keyways prevent the sprocket from rotating on the shaft. This is something that is commonly found in systems that are described as "no slip."  Keyways also allow much greater transmission of force between the shaft and sprocket without slipping. 

Applications & Benefits

The major benefit of using a finished bore for your next manufacturing project is that the sprocket is ready for installation.  The component in question will still be able to carry the load that you need, while also showing higher precision.

Many clients find success using finished bores with standardized applications in their manufacturing environments. Having said that, it's still possible to machine them further to make them more appropriate for any custom application that you might be working with.

Considerations for Specific Industries

One major consideration to make when deciding whether to use plain bores or finished bores has to do with if yours is a business operating in the food and beverage industry. Keep in mind that a finished bore has screw holes, which can easily be filled with liquid or other ingredients if the drive is too close to those materials. From a maintenance perspective, this would essentially introduce a contaminant into the bore itself - leading to potential issues of unplanned downtime (and the increased costs that come with it).

At Illinois Pulley & Gear, we understand that choosing the right components for your mission-critical equipment can quickly prove overwhelming. That's why we've spent years developing a reputation for ourselves as a true partner in your own success in every sense of the term.

We'll take the time to learn as much about your business - and your application - as possible. We'll go over all the options with you in great detail, making sure that you have the most complete picture possible when deciding what to order.

So whether you need replacement parts or items for a custom application, we're here for you. Everything we offer is manufactured in the United States at our very own facility, allowing us to offer fast turnaround times and a level of care and attention-to-detail that you won't be able to find anywhere else.

If you'd like to find out more information about what you should be looking for when comparing plain and finished bore options, or if you're interested in discussing your business' own needs with someone in a bit more detail, please contact the team at Illinois Pulley & Gear today.