located and held in position between the radial step 52 and a set collar 60 which is fixed to the seat 50 with fastener 62 this construction forms a freely pivotable connection between the fixed link 54 and the pivot support arm 32 the vertical fixed link 54 is aligned perpendicular to the surface of the work platform with a roller 31 fig2 and 12 which is rotatably mounted to a flange 33 formed on a lower arm portion 35 of the fixed link 54 the weight of the cutting apparatus fixed to the linkage forces the roller 31 against the inner edge 37 of the guide bar 24 as the roller rolls against the guide bar during a cutting stroke the roller 31 is mounted on the arm portion 35 in a position which orients the fixed link 54 in a perfectly vertical position at all times an abutment surface 39 is formed on boss 41 for limiting the depth of cut of the blade 43 to prevent the blade from cutting deeply into the work platform 18 that is when the threaded adjustable stop rod 48 contacts the abutment surface 39 the downward motion of the pivot support arm 32 as well as the remainder of the linkage is halted in practice the sleeve 34 of support arm 32 pivots within the bushing 56 and further pivots around the support rod 28 in addition the pivot support arm 32 the fixed link 54 and all additional elements connected to them via the linkage discussed below are freely linearly movable along the axis of support rod 28 one of.