The valve manifold is a ½ square brass rod that I chose to turn to round between the areas that hold the valve bodies. It can be left square as Dave did on the first one or even could be made of round stock. The square is easier to fixture.
I made both 4 & 5 valve units and the layout for those is provided on the drawing. For turning the round areas I mounted the part in a collet, and supported the free end on a live center. I just turned to lines drawn on the part.
The 4 valve unit was made to go vertically and was threaded 1/8 npt on the top. The 5 valve unit was fit to an existing 4 bolt flange. The unused ends are threaded 5/16-27 for a plug or additional valve position.
The holes for the valve bodies are .25” and the passageway over the length was drilled .187”, so it would give a nice clean hole at the finish. Once the valve bodies are brazed in the part becomes difficult to clamp so the final cross hole was drilled ¼” with a hand drill, the part being set it in a bench vise.