screw 312 a lock ring 314 a nut 315 and two further lock rings 316 and 317 in accordance with a key feature of the invention the main body 301 is adapted to be mechanically deformed by the incorporation thereof of two slots 323 and 324 that extend perpendicular to each other these slots are perhaps best seen in fig3 b and as shown divide an annular end portion of main body 301 into a fixed part or side 301 a and a movable part or side 301 b as illustrated in fig3 a slot 323 extends inwardly from the circumferentially extending side surface of main body 301 so as to terminate in the main body 301 along a line indicated by the dashed line 323 a portion of which is coextensive with orthogonal slot 324 slots 323 and 324 thus create a movable or pivotable portion 301 b of main body 301 which is capable of pivotable movement or flexing about the base portion thereof if sufficient force is applied thereto thus when the cap screw 312 is tightened against the fixed side 301 a of the cam body 301 the opposite side 301 b of the body 301 defined by the slots 323 and 324 can flex and translate main body 301 includes a central aperture 303 and the inward translation of pivotable part 301 b causes a slight inward distortion of the central aperture 303.