If the test roller (5) hooks on the tip of the tooth or if you need to use some force to move it into the tooth pocket, the sprocket should be replaced.
If the measurement chain (1) slides from the sprocket profile while the handle (6) is under pressure (Fig. III), the amount of wear is excessive. Sprockets with more than 21 teeth are rarely worn out, so they should not cause any problems while in use. Therefore, a check up is normally not necessary. Nevertheless, you can check whether the measurement chain (1) slips off the tooth profile while putting pressure on the grip (6) (Figure III)