How to Choose the Pitch of a Roller Chain?

Have you ever wondered what makes motion transfer smooth in power transmission systems? That’s because of the role of the roller chain. Amongst other things, the pitch of a roller chain determines how smooth and effective it performs. This is why it is vital to choose the correct chain pitch.

In this guide, we will explain what roller chain pitch is and how you can choose the right roller chain pitch to achieve the best performance.

What is Roller Chain Pitch?

The pitch of a roller chain is the distance between the centers of two consecutive pins in the chain. The roller chain pitch is what defines how tightly or loosely the chain links are placed. This directly affects the chain’s overall size, flexibility, and compatibility with the sprocket teeth.

The roller chain pitch is usually measured in inches (according to the ANSI standard) or millimeters (according to the ISO standard). For example, a chain marked as “#40” means it has a pitch of ½ inch or 12.7mm.

Why the Right Chain Pitch Matters

• Chain strength and load capacity: A large pitch means a thicker, stronger chain that can handle heavy loads. If you choose a small pitch for a heavy load, the chain may stretch or fail prematurely. That is why you must select the correct pitch for even distribution of loads.

• Speed and smoothness of operation: Choosing the right chain pitch for the right equipment speed ensures a reliable operation. Smaller-pitch chains, as an example, are more flexible and have an excellent performance with higher speeds and lower vibration with quieter operation. In contrast, a larger-pitch chain is most suitable for slow-moving, heavy-duty equipment.

• Compatibility with sprockets: Not all sprockets have the same chain pitch. Each sprocket has its own specific chain pitch. Using the wrong sprockets for the wrong chain pitch can cause poor meshing, excessive wear, and reduced transmission efficiency.

• Service life and maintenance frequency: The right choice of the chain pitch leads to a lower level of friction and even distribution of the load. This assists in lengthening of the chain and sprocket life as well as reducing the cost of maintenance.

Factors to Consider when Choosing a Roller Chain Pitch

Choosing the correct pitch of a roller chain depends on a variety of factors. Let’s dive into these one after the other.

1. Load and Power Requirements

The load and power requirements are one of the most critical factors to help you choose the correct roller chain pitch.

For heavy-duty, high-load, or shock-load applications, such as conveyors or agricultural equipment, choosing a larger pitch chain is the smartest choice. Its wider link plates and heavier pins provide better strength and durability. On the other hand, in light-duty applications, such as packaging machines, smaller pitch chains are used to maintain compact operation.

When it comes to power requirements, this is also crucial to consider. When higher horsepower is transmitted at a constant speed, the chain must endure continuous stress without chain elongation or failure. Refer to the manufacturer's charts to get the horsepower and rotational speed (RPM) to choose the correct chain pitch, as the wrong pitch can cause inefficiency.  

Therefore, for optimal results, consider the working load and peak load of the chain during operation, and select a chain pitch that accommodates these variations to ensure reliability.

2. Speed of Operation

Consider the speed of operation before choosing a roller chain pitch. When operating faster, the chain is engaged with the sprocket teeth too often, which leads to additional vibration and possible noise. In this case, a smaller pitch chain works best as it provides more links per unit length, enabling smoother movement and reduced noise.

However, extra care needs to be taken as smaller-pitch chains have lower tensile strength and wear resistance under heavy loads. Thus, use the right pitch size in applications where high speed and moderate load exist. For low-speed applications like lifting equipment or agricultural drives, you can use larger-pitch chains for efficient torque transmission.

3. Sprocket Size

The sprocket teeth should also engage the chain pitch of the roller correctly to allow effective transmission of power and its smooth rotation. When there is a misalignment, there is a risk of noise, high wear rates, or mechanical failure. Smaller sprockets (fewer teeth) will result in more wear and lower service life. Therefore, smaller sprockets should be used with smaller pitch chains for continuity.

Conversely, bigger chains are supposed to be used in larger sprockets to give the engagement a smoother feel and distribute the load evenly around the teeth. Thus, ensure that the sprocket pitch diameter is matched with the sprocket size.

4. Center Distance and Layout

The center distance is the spacing between the driving and driven shafts, and this affects the choice of the roller chain pitch. If the distance is too long, the chain must run at a greater length, making it challenging to maintain tension control and alignment. Thus, using a larger pitch chain can minimize elongation. On the other hand, for small-sized machinery, smaller-pitch chains are suitable to provide flexibility and smoother motion.

Evaluate the layout of the chain, as this is what balances pitch, tensioning mechanism, and length to provide vibration. Improper layout can cause uneven load distribution, premature wear, or uneven chain movement. Therefore, consider how the chain will be installed and maintained. Smaller pitches are easy to replace in tight, compact spaces, while larger pitches are easier to inspect and lubricate.

5. Environment and Application Conditions

Considering the operating environment is crucial in choosing the right roller chain pitch. Chains used in dry, indoor settings are different from those used in outdoor settings or areas exposed to dust, moisture, chemicals, and hot temperatures.

For harsh or outdoor environments, or areas exposed to contaminants, such as mining, food processing, or marine applications, choosing a larger pitch chain with corrosion-resistant materials is required. These chains offer greater durability and wear resistance to abrasives or chemicals.  

In areas that experience extreme hot temperatures, smaller-pitch chains are most suitable, while larger-pitch chains are suitable for areas with low temperatures.  

6. Conveyor and equipment design

Every conveyor and equipment system has unique design requirements that require a specific roller chain pitch. The load type, conveyor speed, inclination angle, and operating cycle all affect how the chain performs under mechanical stress.

For example, long conveyor distances need larger pitch roller chains to sustain high tensile forces and provide rigidity. These chains prevent elongation and maintain alignment across extended length.

In contrast, smaller pitch chains are used in compact equipment to offer smoother motion and more accurate positioning. They also enable tight sprocket engagement, reduce vibration, and enhance a quiet operation, which is crucial for high-speed applications.

7. Type of Drive and Motion Characteristics

The type of drive system influences roller chain pitch selection. In a continuous drive system, such as a conveyor system, smaller pitch chains are ideal to maintain a balance between flexibility and strength. In an intermittent drive system, such as a start-stop mechanism, chains are often subjected to continuous acceleration and deceleration. Therefore, larger pitches are suitable to handle the higher dynamic forces and reduce stress.  

In reverse drive systems, such as elevators or automated machinery, the kind of chains needed are those that endure cyclic loading without fatigue. Larger pitch chains with sturdy roller construction are most suitable for absorbing shock.

The drive ratio is also important to consider. High ratios increase tension on smaller sprockets, which can increase stress.

8. Lubrication and Maintenance Accessibility

Larger pitch chains make lubrication easier, as they have more room between components. They allow lubricants to penetrate easily and effectively to reduce wear. Smaller-pitch chains, on the other hand, have tighter tolerances, which can limit oil flow if not properly maintained. Therefore, in systems where lubrication is difficult, larger pitches may be most suitable for long-term reliability.

In high-speed systems, an automatic lubrication system is often used. It maintains consistent lubricant distribution, preventing friction and rapid wear. Chains that run dry often generate excessive heat, causing rapid elongation and failure. The type of lubricant you choose must match the chain pitch.

If a chain is installed in a space that is not easy to reach, choose a roller chain pitch that minimizes maintenance requirements.

9. Alignment and Installation Precision

Alignment between the sprocket shafts and the chain path is crucial in choosing the correct roller chain pitch. If the sprockets are misaligned, the chain experiences stress, wear, noise, and reduced service life. Larger-pitch chains are slightly suitable in this case, but they still suffer efficiency loss if the tension is not aligned. Smaller-pitch chains shouldn’t even be used as they are more sensitive to misalignment.

During installation, correct chain tension is also crucial in choosing the right pitch. Excessive tension can stress the rollers, while too little tension can cause the chain to slip. Proper alignment tools should be used during setup to extend the lifespan of the system.

Tips on How to Avoid Common Mistakes When Choosing Roller Chain Pitch

1. Do not assume a larger pitch automatically means greater strength and durability. Remember, larger-pitch carries more weight and requires more space, even though they have higher tensile strength. If your system operates at high speed or requires smooth motion, a smaller pitch chain may be most suitable to provide better stability.

2. Do not use an old sprocket with a new chain of a slightly different pitch. Even a small deviation can cause improper engagement, excessive noise, or accelerated tooth wear. Verify that the chain and sprocket specifications match, and replace them as a matched set for reliable power transmission.

3. Consider environmental conditions, such as dust, moisture, temperature fluctuations, and chemical exposure, and how they affect the chain’s performance. Choose a roller chain with proper sealing and lubricant to reduce maintenance and replacement costs.

4. Do not overlook lubrication and maintenance needs. Do not use smaller-pitch chains for compact-sized systems except you have planned for accessible lubrication points. Alternatively, you can use self-lubricating chains for situations where manual oiling isn’t practical. Proper lubrication extends the lifespan of the roller chain.

5. It is not new for machinery to evolve over time, thus consider future changes. Choose a chain pitch that has a safety margin to accommodate future adjustments. For instance, choose a chain pitch that accommodates moderate increases in load or speed without exceeding its rated capacity.

6. Remember that chains with smaller pitches are sensitive to misalignment and uneven tension because of their tighter articulation. Therefore, during installation, use precision alignment tools and ensure correct tension for an easy installation process and minimal risk.

7. Do not rely on assumptions or generic charts. Ensure you have access to a reliable manufacturer's data to confirm the material hardness, roller diameter, and fatigue strength of the chain. Consult a reliable manufacturer for detailed load charts, speed ratings, and application support.

Conclusion

Choosing the right roller chain pitch helps you achieve efficient power transmission and extensive service life. By understanding the key factors, you can ensure a reliable and stable performance.

Looking for a reliable manufacturer for your roller chain solutions? Trust Hangzhou Perpetual Machinery & Equipment Co., Ltd to give you expert assistance.

FAQs

How can I calculate the pitch of the chain?

To calculate a chain’s pitch, measure the distance from the center of one rivet to the center of the third rivet and divide the measurement by two.

What is the difference between a 40 and a 41 roller chain?

The main difference between a 40 and a 41 roller chain is their dimension and strength. A #40 chain has a wider and thicker build, while a #41 chain is narrower and lighter.

What chain size is best for speed?

There is no “best” chain size for speed; the best one is the correct size for your specific drivetrain. The chain’s width must match the number of gears for it to work efficiently

What does a 520-pitch chain mean?

A 520-pitch chain means a chain that has a pitch of ⅝ inch and an inner width of ¼ inch.

How can I choose the chain and sprocket size?

To choose the chain and sprocket size, match the chain’s size standard and the sprocket’s pitch. Select the sprocket’s size based on the desired speed and torque.