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.