Plain Bore Sprockets: Specs, Selection & Maintenance Tips

Plain Bore Sprockets Explained: Key Takeaways 

• Plain bore sprockets are essentially unmachined hubs, blank components that can be customized to fit non-standard shafts 
• Their value lies in flexibility: you’re not stuck with factory finished bore specs 
• From shaft compatibility to load resistance, precision here equals performance 

Ever had a sprocket that just wouldn’t fit quite right? If you're dealing with custom machinery, odd shaft sizes, or vintage equipment, you know the struggle. 

That's where plain bore sprockets really shine. They offer more control and options, which means fewer headaches when standard specs just aren't cutting it. 

Here’s what you’ll take away from this guide: 

• What to pay attention to when sizing a sprocket 
• How to pick a plain bore sprocket that fits your setup (and holds up over time) 
• Where plain bore sprockets show up across industries 
• Tips from the pros on how to measure, install, and keep your sprockets running smoothly 

No matter if you’re swapping out an old part or starting fresh with a new project, we're here to provide the right parts and share our expertise to help you get it done just the way you envision. 

9 Specs That Matter for Sprockets 

 When selecting a sprocket, the specifications you choose can really impact your overall setup. It’s important to pay attention to those details to ensure everything works smoothly. 

1.Type 

 When diving into the world of sprockets, one of the key things to understand is that they’re classified based on their hub design.  

The hub is the thicker portion at the center of the sprocket, aside from the teeth. This distinction is important because it affects how the sprocket fits and functions in various machinery. 

According to the American National Standards Institute (ANSI), there are four main types: 

• Type A sprockets are just the flat plate, with no added thickness or hub 
• Type B sprockets have a hub on one side 
• Type C sprockets feature hubs on both sides of the plate, equal in size 
• Type C offset (or Type D) sprockets also have two hubs, but they’re uneven, as one is thicker than the other. This is the most uncommon sprocket type.  

2. Pitch Diameter 

 When you’re looking at a sprocket and chain, the term “pitch” is really important.  

For a chain, pitch refers to the distance between the center of one roller pin and the next; essentially, it’s like measuring from link to link. For a sprocket, you've got three diameter measurements to know: 

• Bottom diameter or the distance across the valleys between the teeth (on sprockets with an even number of teeth) 
• Outside diameter measures from tip to tip of the teeth 
• Pitch diameter is where the sprocket teeth actually grip the chain. It’s also the key measurement for making sure your sprocket and chain work smoothly together. 

3. Caliper Diameter 

If you’re swapping out an old sprocket, especially one with worn or broken teeth, the caliper diameter can be a real lifesaver. 

It’s a measurement taken across the sprocket’s plate without including the teeth 

Since damaged teeth can throw off other measurements, caliper diameter is often your best bet for figuring out what size you’re dealing with. 

4. Hub Diameter 

Right along the same lines, hub diameter measures the thickness of the raised area around the bore on Type B and Type C sprockets. 

It’s the extra material that provides the sprocket with additional strength and structure, so understanding this dimension is crucial for ensuring a proper fit. 

5. Length-Through-Bore (LTB) 

LTB is the total thickness of a sprocket measured straight through the bore, from one outer edge to the other. 

• For Type A, it’s just the thickness of the plate 
• On Type B, it’s from the hub edge to the flat side 
• On Type C sprockets, it runs hub to hub 

LTB refers to the surface contact of the sprocket with the shaft. 

Generally, a longer LTB indicates increased durability, improved alignment, and a more secure fit, making it particularly beneficial in high-load or high-speed situations. 

LTB is critical to check, because if it’s too long the sprocket may not fit in certain equipment where space is limited around the shaft. 

6. Bore Size 

The bore is the hole in the middle of the sprocket (the spot where the shaft goes). 

Getting the right bore size is key. If it’s too small, it won’t fit. Too big, and the sprocket might slip or wobble. 

Either way, it’s bad news for performance. It’s important to ensure the sprocket you choose matches your shaft diameter for optimal performance. 

Also, don’t overlook the tooth pitch because it plays a crucial role in how smoothly everything operates. 

7. Tooth Pitch 

Tooth pitch is all about matching the sprocket’s teeth to the chain it’s driving. Some chains have big gaps between roller pins (large pitch), so they require sprockets with wider, chunkier teeth. 

Others are more compact and pair best with smaller teeth. 

Tooth pitch is basically about how many teeth you have per inch on a gear or a similar component. 

Getting that match right is important because it helps everything operate smoothly. It’s a small detail, but it can make a big difference in performance! 

8. Tooth Count 

Tooth count might seem like a small detail, but it’s key to system performance. 

More teeth mean smoother motion and longer chain life, while fewer teeth increase torque but wear faster. 

It also influences your gear ratio, so the right count helps strike the perfect balance between speed, power, and durability.  

Looking to speed things up and don’t mind giving up a bit of torque? Choose a sprocket with fewer teeth. 

Need more torque and a slower drive? Go with a higher tooth count. Not sure which way to go? We’re always happy to help you pick the right setup! 

9. Number of Strands 

This detail is easy to miss; standard roller chains are typically stocked in up to 4 strands, but custom builds can go as high as 12. 

If you’re running a multi-strand chain, make sure your sprocket has the same number of strands (rows) to match. 

A single-strand sprocket is your everyday go-to, but if you’re looking to move more power without changing your setup, a multi-strand sprocket, paired with multi-strand chain is the way to go. 

By using roller chain that is 2 or more rows wide, you can generate significant torque from one shaft while ensuring smoother operation under heavier loads. 

Understanding Plain Bore Sprockets 

A plain bore sprocket is a unique type of sprocket that features an unfinished, solid bore. 

This means it hasn’t been machined to fit a specific shaft size—think of it as a "blank canvas" waiting for your personal machining touch. 

It’s a great option if you’re looking to customize your setup just the way you want it.  

Applications for Plain Bore Sprockets 

Plain bore sprockets show up in more places than you might think, including: 

• Industrial machinery: These sprockets are a solid choice for conveyor systems and heavy-duty machines, especially when you need a perfect fit. 
• Agricultural equipment: From tractors to harvesters, plain bore sprockets are great when you need to fine-tune components for specific tasks out in the field. Some old-school farm equipment requires sprockets with uncommon bore sizes or keyways, making them the perfect candidate for a custom-machined plain bore sprocket.  
• Construction equipment: Think bulldozers, excavators, and portable crushing plants. Plain bore sprockets are often machined to fit unique shaft sizes on rugged machines that take a beating on the job site. 
• Food processing equipment: In stainless or non-corrosive materials, plain bore sprockets can be machined to fit custom conveyors, slicers, and automated packaging lines, all while keeping your line food-grade and protecting against corrosion. 
• Mining operations: Whether it’s in crushers, feeders, or material conveyors, the ability to machine a plain bore sprocket to spec makes it easier to match existing shafts and reduce downtime in remote or high-demand environments. 

Factors To Consider When Choosing Plain Bore Sprockets 

Before you choose a plain bore sprocket, make sure you’ve checked off these essential details. 

• Bore size: Since plain bore sprockets come unmachined, you’ll need to match the bore to your shaft. Too loose or too tight, and you’re asking for trouble, like slippage or misalignment. 
• Length-through-bore (LTB): This tells you how much contact the sprocket will have with the shaft. A longer LTB usually means more stability and better performance under load. 
• Hub type: Type A, B, C, or D? Each one has a different hub layout, so make sure the style fits how and where the sprocket will mount. 
• Tooth count and pitch: You’ll want the tooth pitch to match your chain, and the number of teeth will affect how much torque or speed you get. It’s all about finding the right balance. 
• Material and finish: If you're working in a harsh environment (for instance, wet, dirty, or corrosive settings), go for something like stainless or nickel-plated steel. In cleaner setups, standard carbon steel usually does the trick. 
• Load demands: Heavier loads call for tougher sprockets. Make sure it’s built to handle the pressure, especially around the bore and hub. 
• Machining needs: One of the perks of plain bore sprockets is customization, but keep in mind that precision matters. If you're not boring it yourself, choose a machine shop that can modify it with precision. Don’t have a machine shop that you trust? We can help with that!  

How To Measure, Install, and Maintain Plain Bore Sprockets 

Getting the most out of a plain bore sprocket starts with proper sizing, careful installation, and regular upkeep. 

Start on the right foot with these expert tips: 

Measurement 

• Start with your shaft diameter: Grab a caliper and get it as exact as possible. Even a slight mismatch can cause the sprocket to wobble or slip on the shaft. 
• Check the keyway: If your setup uses a keyway, make sure you know the right width and depth for that too, as you’ll need those specs machined into the sprocket. 
• Measure LTB and hub diameter: This helps confirm the sprocket will seat properly and won’t get in the way of surrounding components. 
• Don’t forget tooth count and pitch: Matching them to your chain is what keeps the system running in sync. 
• Decide how many setscrews you will need to hold your sprocket on the shaft: Higher torque applications typically require a thicker keyway and larger than standard setscrews. Plain bore sprockets do not come with keyways or set screws, so you will be able to customize them exactly to your liking.  

Installation 

• Get the bore machined correctly: If you’re not doing it yourself, work with a shop that can match your exact shaft diameter and keyway dimensions to ANSI or OEM specs. Even slight inaccuracies can lead to slippage, vibration, or premature wear. 
• Align it carefully: Use a straight edge or laser to line up the sprocket with the others in your system, as even a small misalignment can cause major wear over time. 
• Secure it firmly: Use set screws, locking collars, or other hardware to keep the sprocket from shifting once it’s in place. 
• Set the right chain tension: Too tight, and you’ll strain the whole system. Too loose, and the chain could jump or wear unevenly. 

Maintenance 

• Inspect regularly: Keep an eye on hooked or worn-down teeth, an elongated chain, or any wobbling around the bore. Catching these early warning signs can save you from bigger problems down the line. 
• Keep the chain lubricated: The sprocket itself doesn’t need lube, but a dry or dirty chain will chew through teeth fast. 
• Clean it up: Dirt and grime love to sneak into the gaps between your chain and sprocket teeth. And if you let it sit, it’ll wear things down fast. A quick wipe with a soft brush or cloth can make a big difference. If it’s really gunked up, go ahead and use a mild degreaser. 
• Replace the chain and sprocket together when possible: Pairing a worn chain with a brand-new sprocket (or the other way around) might seem fine at first, but it usually just speeds up wear on the new part. Think about it like putting brand new brake pads on your car, without replacing your old, crusty rotors. It would be fine for a bit, but before you know it, your brand-new brake pads will be worn out. 

Find Your Next Plain Bore Sprocket (and More) at USA Roller Chain & Sprockets 

Looking for a plain bore sprocket that matches your set up? We make it easy at USA Roller Chain & Sprockets. 

Our sprockets come in a wide range of sizes and styles, and because they’re plain bore, you can machine them exactly how you need. 

Check out some of our best-selling plain bore models: 

• 40B11 Sprocket: A solid pick for lighter-duty applications or general use 
• 60B14 Sprocket: Tough, versatile, and easy to machine to your specs 
• 80B17 Sprocket: Ideal for medium-load systems 

Need a chain to go with it? No problem! We carry a full line of roller chains to match. 

Not sure which one fits your setup? We’re Here to Help 

Plain Bore Sprockets: FAQs 

What is a sprocket? 

A sprocket is a tough, toothed wheel that works together with a chain. As the sprocket turns, its teeth latch onto the links of the chain, pulling it along and setting other connected parts into motion. 

This setup efficiently drives everything from conveyors to heavy machinery by controlling rotational movement. 

What’s the lifespan of a sprocket? 

If you keep up with maintenance, industrial chain and sprockets can usually last between 10,000-15,000 hours, but this varies greatly from application to application.  

What’s the difference between a plain bore and a finished bore? 

A plain bore is an unmachined hole that needs custom boring and locking hardware to fit your shaft. A finished bore comes ready to install, already machined with a keyway and set screw holes. 

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