Replace sprocket segments by removing the worn segments, cleaning the mounting, fitting new segments in the correct tooth pattern, and torquing the bolts to the published values with a re-torque after initial use.
Related reading: for full sprocket replacement, see our mini excavator sprocket replacement guide.
Sprocket Segment Guidance from AFT Parts
- Source: AFT Parts — sprockets and undercarriage components.
- Scope: Sprocket segment replacement, bolt torque, and tooth pattern
- Fits: CAT, Komatsu, Kubota, Bobcat, Hitachi, Takeuchi, and more.
- Application coverage: BC forestry, roading, construction
- Verified: part number and machine serial before dispatch.
Segments vs Full Sprocket: When Each Replacement Is Right
Replace segments when the teeth are worn but the sprocket hub and mounting are sound. Replace the full sprocket when the hub, spline, or mounting is damaged.
Segments are the economical choice when the wear is in the teeth only. The decision is made by inspecting the hub and mounting, not by the tooth wear alone.
Removing Old Segments Cleanly and Inspecting the Hub
Remove the segment bolts with the correct sockets and lift the worn segments clear. Clean the mounting surface so the new segments seat flat.
Inspect the hub and bolt holes for damage before fitting new segments. A worn or dirty mounting face leaves the new segments running crooked.
Keep the removed segments and bolts organized by position while the ring is open. The old hardware and the new kit are compared against the part number before the new segments are fitted, and a photographed mounting face gives the supplier the reference for any fitment question.
Bolt Grades and Torque Sequence: The Ring's Load Path
Use the specified bolt grade and torque the segments to the published values in the correct sequence. Segment bolts carry the drive load, and the torque sequence keeps the ring even.
Use a calibrated torque wrench and mark the bolts after the initial torque. A segment that is over- or under-torqued shifts under load and wears the teeth unevenly.
The torque sequence is written for the ring as a whole, so follow it across the full set of segments rather than position by position.
Aligning Segments So the Tooth Pattern Stays Continuous
Fitting segments requires matching the tooth pattern across the segment joints. Align each segment so the tooth spacing is continuous around the sprocket.
Check the pattern after fitting by rotating the sprocket and looking at the joint teeth. A misaligned segment hooks the chain and wears fast.
Fit the full ring before final torque so the segments settle as a set: a segment torqued alone can hold the joint open, while a ring brought down together seats each tooth into the same pitch circle. The ring fit is what keeps the chain engagement smooth across the joints.
Why Re-Torquing After Initial Use Is Not Optional
Re-torque segment bolts after the first hours of operation as the manufacturer recommends. New segments and bolts settle under load.
Mark the bolts and check them on the re-torque schedule. A loose segment is a chain hazard, not just a sprocket problem.
The re-torque is also the moment to re-check the tooth pattern: rotate the sprocket a full turn after the re-torque and confirm the joints are still aligned. A segment that moves between the initial torque and the re-torque was not seated properly and should be corrected before the machine works a full shift.
Common Segment Mistakes: Reused Bolts, Skipped Sequence, Mixed Sets
The common mistakes are reusing worn bolts, skipping the torque sequence, misaligning the tooth pattern, and missing the re-torque. Each one shortens the segment life and wears the chain.
Forcing a segment into place or mixing segment brands can also throw off the tooth pattern. Fit matched segments from one set.
Safety note: segment bolts carry the drive load — use the OEM torque values for your model, follow the sequence, and re-torque as the manual requires.
Common Mistakes
- Reusing worn segment bolts.
- Skipping the torque sequence.
- Mixing segment brands and breaking the tooth pattern.
- Missing the re-torque after initial use.
Conclusion
Sprocket segment replacement is a details job: clean the mounting, use the right bolts, torque in sequence, align the tooth pattern, and re-torque after initial use. Fit matched segments and the ring wears evenly and protects the chain.
Key Takeaways for Canadian Operators
- Replace segments only when the hub and mounting are sound.
- Clean the mounting and use new bolts at the specified grade.
- Torque in sequence and mark the bolts.
- Align the tooth pattern across the segment joints.
Questions to Ask Before You Order
- What are the segment part numbers for my sprocket and serial number?
- Does the kit include bolts and torque specifications?
- Should I replace all segments at once?
Browse the Sprocket collection and the 1243296 CAT sprocket for your machine.
Frequently Asked Questions
When should I replace sprocket segments instead of the full sprocket?
Replace segments when the teeth are worn but the hub and mounting are sound. Replace the full sprocket if the hub, spline, or mounting is damaged.
Can I reuse the segment bolts?
No. Use new bolts at the specified grade. Segment bolts carry the drive load and reused bolts loosen under load.
How do I align sprocket segments?
Fit each segment so the tooth spacing is continuous across the joints, and rotate the sprocket to check the pattern after fitting.
Can I replace one segment at a time?
Replace segments in matched sets where the wear is similar. A single new segment beside worn segments can hook the chain.
How tight should segment bolts feel by hand?
Feel is not a torque method. Use the OEM torque values and a calibrated wrench, then re-torque after initial use.