function r_from_dia(d) = d / 2; module rotcy(rot, r, h) { rotate(90, rot) cylinder(r = r, h = h, center = true); } difference() { sphere(r = r_from_dia(size)); rotcy([0, 0, 0], cy_r, cy_h); rotcy([1, 0, 0], cy_r, cy_h); rotcy([0, 1, 0], cy_r, cy_h); } size = 50; hole = 25; cy_r = r_from_dia(hole); cy_h = r_from_dia(size * 2.5);