infty = 100;
eps = 0.01;

tube_d = 6 + 0.7;
hole_h = 6;

wall = 1;

outer_d1 = tube_d + 2*wall;
outer_d2 = tube_d + 2*wall + hole_h * 0.7;
top_h = outer_d2/4;

difference() {
	hull() {
		cylinder(r1 = outer_d1/2, r2 = outer_d2/2, h = hole_h, $fn = 16);
		translate([0, 0, hole_h]) scale([1, 1, top_h*2/outer_d2])
			sphere(outer_d2/2, $fn = 16);
	}
	translate([0, 0, -eps])
		cylinder(r = tube_d/2, h = hole_h + eps, $fn = 16);
}