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In power transmission and conveying systems, the chain is a critical and durable component. Whether for routine maintenance, replacement, or troubleshooting, accurately determining a roller chain's pitch—its fundamental dimension—is the essential first step. An incorrect measurement can lead to ordering the wrong replacement, causing machine downtime, accelerated wear, and potential drive failure.
This guide clarifies the correct procedure for measuring roller chain pitch, ensuring precision and reliability in your maintenance operations.
Why Pitch Measurement is Critical
Roller chain pitch is defined as the distance between the centers of two adjacent link pins. It is the primary identifier for roller chain size (e.g., ANSI #40, #50, #60 or ISO 08B, 10B, 16B). Using a roller chain with an incorrect pitch will not properly engage with the sprocket teeth, leading to:
Jumping and Ratcheting: The roller chain will not seat correctly on the sprocket.
Catastrophic Wear: Both the roller chain and sprocket will wear out rapidly.
System Failure: Can result in chain breakage and damage to machinery.
Tools You Will Need:
A high-quality vernier caliper or micrometer (for best accuracy).
A ruler or tape measure (for a quick, less precise check on longer chains).
A clean rag to remove dirt and grease from the roller chain.
Step-by-Step Measurement Procedure
1. Clean and Prepare the Roller Chain
Wipe a section of the roller chain clean, especially the pin and roller areas. Dirt and hardened grease can significantly affect measurement accuracy.
2. Identify the Measurement Points
For Roller Chain, the pitch is measured from the center of one link pin to the center of the next link pin. Do not measure from the outside of the sidebars, as this is not the true pitch.
3. The Accurate Method (Using Calipers)
Extend a straight section of the roller chain.
Using your calipers, measure the distance between the inside surfaces of two adjacent link pins.
Add the diameter of one link pin to this inside measurement.
Formula: Pitch = (Inside Distance Between Two Pins) + (Diameter of One Pin)
This method directly yields the center-to-center distance, which is the true pitch.
4. The Direct Reading Method (Using a Pitch Gauge or Specialized Caliper Jaw)
Specialized roller chain pitch gauges (like feeler gauges for chains) can be inserted between rollers. The gauge that fits snugly indicates the pitch.
Some digital calipers have a concave jaw accessory designed to seat on the pins for a direct center-to-center reading.
5. The Long-Span Method (Using a Ruler – Less Precise)
Stretch out a section of the roller chain (e.g., 12 or 24 links).
Measure the total length between the centers of the first and last pins in your selected span.
Divide the total length by the number of links in the span. This average minimizes error from individual link wear.
Formula: Pitch = (Total Center-to-Center Length of N Links) / (N)
Common Pitfalls to Avoid:
Measuring Over Worn Pins: In a severely worn roller chain, the pins and bushings are eroded, making the pitch longer. Always measure in an unworn section if possible, or use the long-span method to average it out.
Confusing Pitch with Other Dimensions: Roller chain width (between inner plates) and roller diameter are different, crucial specs but are not the pitch.
Not Consulting Manufacturer Tables: Once measured, cross-reference your finding (e.g., 0.500", 0.625", 0.750") with standard chain pitch tables to identify the exact chain size.
Pro Tip: For the most critical applications or highly worn chains, the long-span averaging method using a precise measuring tape is often the most reliable way to determine the nominal pitch.
For further information or technical support, please contact us.
