When I was thinking about the design for the jig, the idea for which came from Peter Alexander's "Gunsmith of Grenville Co." book, I took out a half dozen or so castings - some investment, and some sand castings, and measured the lugs. Knob Mt.'s guard was the thinnest at just under 1/8" thick. So, I'll file them all to fit this jig believing all the time that 1/8" is lots of brass for the purpose. On many sand castings in fact, the lugs are not perpendicular to the forward and read returns, and are often off centred, so they need filing anyway. I was pleased to find that you don't have to run the screws in too hard to clamp the lugs firmly. And the guard does not move in the slightest in the jig. Best of all, it does not vibrate, though I file to centre from each side. As I said prior, this particular guard was so smooth, that I did not have to use a rasp to remove flaws or irregularities.
It is such a pleasure to use a jig that works so well...don't know why I waited so long to make one.
