of smooth bore 70 is not in registry with smooth bore 80 of outer collar 20 it should be understood that the centerline b u2014 b of smooth bore 80 of outer collar 20 is parallel to but slightly offset from the centerline c u2014 c of outer collar 20 in the preferred embodiment the offset is in the approximate range of 0 012 to 0 016 inches preferably about 0 014 inches therefore when outer collar 20 is rotated such that ridge 84 is out of longitudinal alignment with protrusion 72 of inner collar 16 smooth bore 80 of outer collar 20 is offset by an increasing distance from smooth bore 70 of inner collar 16 as outer collar 20 is rotated smooth bore 80 thereof applies side force to wand 18 and forces it against a side of smooth bore 70 of inner collar 16 in the preferred embodiment the smooth bore 80 of outer collar 20 is slightly larger than the smooth bore 70 of the inner collar 16 preferably the diameter of smooth bore 80 is 0 290 u00b1 0 002 inches and the diameter of smooth bore 70 is 0 243 u00b1 0 002 inches the diameter of the wand 18 is preferably approximately 0 236 inches and wand 18 therefore slides snugly but without interference within inner collar 16 when outer collar 20 is rotated to a position where ridge 84 thereof is aligned with protrusion 72 of inner collar 16 smooth bore 70 is in registry with but not centered on smooth bore 80 of outer collar 20 when outer collar 20 is rotated away from the position in which ridge 84 is aligned with protrusion 72 shear force is applied to wand 18 from misalignment.