$fn=90;
use <threads.scad>;

difference() {
  
  union() {
    hull() {
      translate([0,0,10]) rotate_extrude() translate([30/2-2, 0]) #circle(r=2);
      cylinder(d=30, h=10);
    }
    for(i=[0:360/12:359]) rotate([0,0,i]) translate([15,0,1]) hull() {
      translate([0,0,8]) sphere(d=2);
      sphere(d=2);
    }
  }
  render() metric_thread(
    diameter=27,
    pitch=3.5,
    thread_size=2,
    length=8,
    groove=true
  );
  translate([0,0,8]) cylinder(d=26.5, h=2);
  translate([0,0,-0.01]) union() {
    cylinder(d=19, h=20);
    cylinder(d1=27, d2=26, h=1);
  }
}