I finally got my index pin block made. After failing to find any suitable aluminum locally, I had to get it online. I used your affiliate link with Online Metals, so you should get a royalty from the sale. I made the block as simply as I could; the brass pin fits tightly enough that I don't think it needs a clamp. The diameter of my pin (3/16") was just on the edge of being too big: three holes stacked together leaves very little metal between them. If I ever make another one I'll use a 5/32" pin and holes.