enhance the ability of the hub to provide a concentric drive and reduce surface wear the width of the splines on the roll which corresponds to depression 52 on the hub is about u00bd the width of surfaces 54 of hub 50 because of clearances required between splines 74 on roll 20 and depressions 52 on hub 50 most of the force required for concentricity arises from surfaces 54 of hub 51 the presence of splines 74 and recesses 52 assures that shaft torque is applied to roll 20 the method of expanding hub has been explained using only one of the methods described in u s pat no 5 700 233 of course other methods will be obvious the shape of the engaging surfaces of the hub with the roll is important it will be found that a large portion of the hub surface is formed into the cylindrical mating surface of the hub so that concentricity is assured between the hub and the roll because of the frequency of roll replacement in modern steel mills this method of mounting and demounting the rolls on the driving capstan is swift and easy and is accomplished with a minimum inconvenience and few tools surface wear of the roll capstan interface is practically non existent and any small amounts of wear at the interface is easily compensated for by the expanding capstan other advantages of this mounting technique and apparatus is the shortening of.