Roller chain is a precision-made item that is manufactured to very tight tolerances.
This means that when it is first manufactured it can be wrapped around the sprocket and the rollers will fit perfectly into the seating radius of the sprocket.
In use, however, roller chain will regrettably elongate due to wear. The amount of roller chain wear is totally dependent on the type of chain application, the loads being exerted on the chain, the lubrication used and the maintenance regime employed.
Dependant on all these factors the roller chain will either wear slowly or rapidly.
As roller chain elongates it will be found that the individual rollers will start to contact the flanks of the sprocket teeth rather than fitting perfectly into the seating radius. This gradual process then leads to several unwanted roller chain problems, such as:
As the roller chain rollers contact the flanks of the sprocket teeth under load, the impact will cause these surfaces to become worn and this will gradually result in ‘hooked’ sprocket teeth, which will then lead to total failure of the sprocket teeth.
The roller chain application will become increasingly very noisy and inefficient. Ignoring the noise of a badly worn roller chain setup is one thing but as the efficiency of the roller chain drive diminishes the costs associated with running the system will inevitably rise.
As a roller chain drive wears there is an increasing amount of vibration felt within the chain setup. As this roller chain vibration becomes more acute it will lead to problems with other associated equipment.
If roller chain is being used in pairs for conveying or singularly for an indexing application then any significant amount of roller chain wear will rapidly lead to roller chain mismatch or roller chain misalignment. These types of difficulties are likely to lead to bigger problems with any associated equipment.
By measuring roller chain for wear, at regular intervals with a chain gauge, it will become clear that the amount of increase in length can be predicted and the roller chain can be routinely scheduled for replacement. As a general rule of thumb most roller chain drive applications can be considered to be worn out at a length increase of approximately 1.5 per cent.