type that is indicated in general as 190 is located that constitutes the manual control member of movement of the transverse slide 160 on the cylindrical guides 150 a movable platform 181 is connected to the transverse slide 160 on the movable platform 181 there are cylindrical sliding guides 151 for a lengthwise slide 161 having an approaching stroke and a moving away stroke with respect to a shaping pulley 1 along a lengthwise direction n of movement of the grinding belt 2 a workpiece vice 20 is mounted revolving on the lengthwise slide 161 as in the first embodiment the workpiece vice 20 has a base 21 which is provided with a slot 22 in the form of a circle arch and a securing screw 23 to the lengthwise slide 161 for setting the angular position of the workpiece vice 20 with respect to the direction n of movement of the grinding belt 2 further the lengthwise slide 161 is constrained to a straight linear cam 30 that can swing in its angle coplanar to the parallel sliding planes of the transverse and lengthwise slides 160 161 the swinging straight linear cam 30 is formed by a channel 31 that is pivoted at right angles on the fixed platform 80 of the worktable 60 by means of a rotation pin 32 fig4 as shown in fig5 the channel 31 has off centre a setting pin 33 that is received into a circle arch.