Measuring wear on drive sprocket A is somewhat difficult.
This is because, under routine working conditions, wearoccurs in such a way as to remove any valid, pre-existing reference for establishment of the extent of wear itself.
It is not, therefore, possible to provide precise values and it isalways necessary to compare with the teeth of a new wheelof the same type.
As a general rule, it can be stated thatthe toothed wheel needs replacing when wear has reachedthe limits illustrated in the diagram.
Wear is never uniform:take the point at which it is most accentuated as yourreference. Putting maximum admissible wear into figures,it can be calculated as 0.03% of the pitch of the catenarythat is coupled to the toothed wheel. Measure using a depthgauge B.