I’ve held on to my used flints with the hope of one day figuring out how to sharpen them. At $2.50 to $3.50 a pop, things can add up (especially since my Charleville chews flints like a teenage girl through a pack of bubble gum).
I’ve tried a few techniques such as napping with a flint hammer and snipping the edge of the flint with needle nose pliers. But these techniques were iffy at best. I would only manage to get one or two more good sparks before the flint was completely useless.
I finally came across a video with an interesting technique here:
Capandball uses a small brass rod that is tapered at the end. With this technique I was able to sharpen my old flints with great success! In fact, I think they are sharper now, but probably less structurally sound (more likely to disintegrate). Nevertheless, this is exactly what I was looking for. Many thanks to you good sir!