Crius, thanks. It took me a while to get this one more or less right. Those clamps are marvelous. I have several now. This was my first attempt at
making a fixture like this but not the first for drilling tracks. I made my own tool steel drill guides and that was the most trying aspect. I tried to harden a first attempt for the upper and it didn't end well. The inner portion of the forward guide is sort of hard. I just recently purchased an electric lab furnace that can go to about 1900F and next time I'll use it. I don't have the specs on the steel I have but I'd try oil bath hardening first and water second if
oil doesn't work. The other challenge is that the tracks castings, I didn't make them, have variations which required modifications to the fixture to allow for them. The castings I believe were made by different founders and there's different amounts/types of cleanup required but I made the holding area more generic. This fixture isn't perfect but it is ok and right now allowing me to make good progress.