72 a drive miter gear 78 is carried by the lower end of drive shaft 74 drive miter gear 78 meshes with the driven miter gear 70 and transmits rotary motion to roller shaft 52 as seen in fig1 a front cover 73 and a rear cover 75 are provided for the miter gears 70 and 78 the covers 73 and 75 are secured to the main bracket 34 by screws 77 that are threaded into threaded bores 79 in the main bracket 34 the preferred embodiment includes a one piece plastic cover for the miter gears 70 and 78 the front roller bracket 60 see fig6 and 6a includes a pair of hubs 82 and 84 at its forward end in which is journaled a front roller shaft 80 the hubs 82 and 84 have sets of needle bearings to minimize friction in these journals a front roller 86 and a front pulley 88 are secured to front roller shaft 80 for rotation therewith the front pulley 88 is aligned with rear pulley 66 and a drive belt 90 extends over the aligned pulleys 88 and 66 such that the rotary motion of rear roller shaft 52 is transferred to the front roller shaft 80 in the preferred embodiment the pulleys 66 88 and the belt 90 are of the sprocket type that have grooves and ridges on their engaging surfaces this sprocket type drive not only provides a more positive drive connection between the pulleys and the belt but also ensures that the front roller 86 and rear roller 50 are synchronized the front roller bracket 60 has an inclined u shaped portion 92 that includes a hub 94 at its forward.