boltD = 4.8; boltheadD= 9; boltarea=3; width=17; difference(){ union(){ cylinder(d=width, h=boltarea, $fn=60); translate([0,0,boltarea]) cylinder(d1=width,d2=width-5,h=boltarea,$fn=60); } cylinder(d=boltD, h=boltarea, $fn=60); translate([0,0,boltarea-1]) cylinder(d=boltheadD,h=boltarea+1,$fn=60); }