book thicknesses three drive slide bar shaft links 48 have one end mounted on the adjustment shaft 40 the other ends of the links 48 carry a bender linkage shaft 50 both ends of the links 48 have bearings mounted therein so that the shafts can rotate in the links the bender linkage shaft 50 carries three drive slide bar shaft links 52 a drive linkage shaft 54 is mounted in the opposite ends of the links 52 again there are bearings in the links 52 which allow the drive shaft 54 to rotate in the links two adjustment bar shaft links 56 are connected at one end to the drive shaft 54 and at the other end to an adjustment bar shaft 58 thus it can be seen that the bender shaft 50 the drive shaft 54 and the adjustment bar shaft 58 are linked to the head adjustment eccentric shaft 40 by means of the various links 48 52 and 56 rotation of the eccentric bearings 42 and 44 will then alter the positions of the shafts 50 54 and 58 the ends of the bender shaft 50 drive shaft 54 and adjustment shaft 58 extend beyond the upright frame members 20 the bender.