How to Tell When Worn Sprockets Have to Go
Sprockets that have worn beyond a certain point will cause rapid chain wear and should be replaced as soon as possible. But how much wear is too much, and what sort of visual inspection can you carry out to determine this?
If you look at the faces of the sprocket teeth you'll see an indication of the amount of wear that has already occurred. This will be seen as a polished worn strip, about the pitch circle diameter, on each of the teeth as shown in the diagram.
If the depth of the wear, X, has reached a value equal to 10% of the dimension Y, then the sprocket has reached the end of its life and needs to be replaced. It's worth pointing out that low cost, poor quality sprockets on most industrial applications are a false economy. A good quality sprocket should last through the life of several chains before anything like the amount of wear shown here will have occurred.
When changing sprockets it's a good time to check the alignment of both the sprockets and the shafts to which they are fitted. Misaligned sprockets is another factor in premature chain wear. Accurate alignment of shafts and sprocket tooth faces provides uniform distribution of load across the entire chain width and contributes substantially to achieving maximum life. Also, use a straight edge across the machined faces of the sprockets in several different positions, if possible, as a check against wobble.
Tip: a nylon line or laser sight tool is a good substitute for a straight edge, particularly for drive systems with long centre distances.
Should end-wise float of shafts be present make due allowance so that sprocket alignment is correct at the mid position of float. When alignment is correct within closest practical limits, drive the keys home and make a final check on sprocket alignment. If you're fitting new chain at the same time don't forget to correctly lubricate it. The lubrication that's on the chain when it comes out of the box is only sufficient to prevent corrosion and aid initial bedding in.
There are some industrial applications on which even standard chain won't offer the performance and wear life of one selected from our range of Solution Chains. Factors like the inability to lubricate, hostile environments, regular wash downs and arduous conditions will reduce the performance of standard chain and cause it to wear rapidly.
Discuss your application with our skilled team today.
Renold have developed a range of High-Performance sprockets that are induction harderened, further corrosion resistant and surface treated for a longer life. Found out more here