Bearing in openscad

difference(){
difference(){
cylinder(6,8,10);  //outer part
cylinder(6,7,9);   //inner part
}
for ( i = [0 : 18] ) //loop to make cylindrical holes around bearing
{
    rotate( i * 360 / 19, [0, 0, 1])
    translate([0, 8, 2])
    cylinder(2,1.5,1.9);
}
}

for ( i = [0 : 18] ) ////loop to make cylinder in cylindrical  holes around bearing
{
    rotate( i * 360 / 19, [0, 0, 1])



translate([0, 8.5, 2])
cylinder(1.9,1,1);
}