use height = 110; bottom_d = 70; top_d = 170; facets = 40; bottom_r=bottom_d/2; top_r=top_d/2; thickness=2; difference() { cylinder(height, bottom_r, top_r, $fn=facets); translate([0,0,-0.01]) cylinder(height+0.02, bottom_r-thickness, top_r-thickness, $fn=facets); } nut("M42x3", turns=2, Douter=bottom_d);