You are working on a starter motor that lacks pep and drags when turning. You know the battery and all connections are good.
Now, to check if starter armature is rubbing the field coil when turning. Hold a safety razor blade lightly between thumb and forefinger resting hand on the motor housing with blade slightly above housing and run the starter motor.
If armature rubs at any point the blade (SPST above motor case) will be attracted to motor housing.
