The circular cam surface 30 of the flange 27 of U plate 24 circles about screw 28 and extends or projects in one direction on one portion 30 of the circle and projects in {HEAD ~ the opposite direction} in {TAIL ~ the opposing portion} 30 of the circle 
The circular cam surface 30 of the flange 27 of U plate 24 circles about screw 28 and extends or projects in one direction on one portion 30 of the circle and projects in { HEAD ~ the opposite direction } in { TAIL ~ the opposing portion } 30 of the circle
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