another idea. use 1/2 aluminum square stock the length of the rod you want to be held in the stock to make bushing. Drill and tap shallow holes #10 oe # 8 screw in the four corners on one side of the

Test drill from top and bottom to locate the aluminum bedding block. Look for aluminum shavings to determine depth. Mill on the side that gives you room for half inch aluminum square stock and still be able to fill and sand to the original contour ....if possible. mill milling a half inch spot/key 1/8th inch the bedding block. Drill 4 screws holes on each end/corner of the square bushing to match tapped holes.

Mount and fill. Epoxy mount in the bushing. this will make your project bullet proof and could be done on any mill with some good cribbing and a good vice.