Shaft tolerance is the amount of allowable difference between the size of collar or coupling and the size of the shaft that will still allow the component to function. Ideally, a ¾” collar will be used on a ¾” inch nominal shaft. The closer to nominal the better – if the difference is too great, the collar may not even clamp. A difference of even ½ millimeter is quite high. Climax bore tolerances can be found in our catalog and online.