Drive pulley M3 hole

[jmgiacalone]

The drive pulley M3 grub screw hole consists of a cylinder and cube. Where these transition there is a step. The following code gets rid of the step:

    //entrance
    translate([0,-3,15]) cube([5.8,7,3],center=true);
    //nut
    translate([0,0,13.6]) rotate([0,0,30])cylinder(r=5.8 / sqrt(3),h=2.8,$fn=6);
    //grub hole
    translate([0,0,9]) cylinder(r=3.3/2,h=10);