A number of years ago, I decided to try adding a piece of flourescent orange fiber optic material from an archery sight to the front sight on a Thompson Center flintlock rifle, because the original was often hard to see in dark woods in early morning or late evening on overcast winter days.
I picked up a spare front sight at a gun show for the project. The bead section was about .100" in diameter. I filed away about 3/8" of the long bead in the middle, for ambient light to illuminate the fiber optic material. Then I had to drill a tiny hole centered in the bead sections remaining. As I recall, I used a #54 drill bit, which is .055" diameter, for the fiber optic to slip through.
I used a Unimat SL lathe/mill/drill to drill the hole, and carefully aligned the sight in the Unimat vise vertically. It was surprisingly easy to drill this small diameter hole through roughly 1/2" total of investment cast steel. I used high rpm, light pressure, and Brownell's Do-Drill cutting lube. I then blackened any shiny metal with Oxpho Blue, and inserted the fiber optic material. I secured it in place by quickly heating and melting both ends with a small flame from a butane pencil torch.
It worked great, and was easier than I thought it would be to drill that tiny hole, perfectly centered lengthwise through the front sight. So I think it would be just as easy to drill a hinge pin hole through a piece of mild steel, and then cut and file away everything that doesn't look like a rear sight blade. In any event, I'd begin by drilling the hole, and then shape the blade. With a very steady hand and good eyes, it might even be possible to drill the hole using a Dremel rotary tool, if you had the right collet to hold the bit. But my little Unimat made it relatively easy.
