Has anyone ground a coin flat to use as an edge burnisher?

I made one of these a couple years back after seeing the same trick, and honestly the grinder isn't even the easiest route. I flattened mine by sticking a quarter to a granite surface plate with some spray adhesive and rubbing it in circles on progressively finer sandpaper, starting around 120 and working up to about 600. Takes maybe twenty minutes, no heat, no risk of chewing up the coin with a grinding wheel. Any flat reference surface works, a piece of float glass or even a known-flat tile is fine. You just want the face flat and you want the edge of the coin broken slightly rounded so it doesn't dig little lines into your burnish.

I'm not convinced that the manual sanding method is actually the easiest route. You're relying too much on consistent force and grit selection to achieve a perfectly flat surface, which isn't a reliable technique for serious work. If precision is what you're aiming for, jumping straight to a proper bevel set or a precision sharpening jig is a much better investment. Those tools provide repeatability and consistency that you just won't get by rubbing a quarter on some tile for twenty minutes. That's just too much guesswork.

I've been doing this kind of leatherwork since before these hacks became popular. While the coin method is fine, you are chasing a perfect flatness that a simple wooden slicker and some elbow grease can often match. My own setup always had a few pieces of scrap hardwood lying around the bench. I whould slowly sand them down on a flat workbench untill one felt like it had the right heft and contour for my specific job. The key is finding a piece that gives you consistent contact pressure, not a mathematically perfect bevel. What kind of leather are you planning on using for the project?

I started using something a while ago that completley changed my process when using these types of tools. Instead of trying to grind them perfectly flat, I actually went with a piece of old window glass that I just rounded down. My edge work always felt much better with that rounded profile beacuse it gave a continuous, rolling pressure across the leather instead of a sharp, flat line. It took some careful shaping to get the edges right but the final finish on the leather is a lot smoother with it.

I used the side of a thin metal file for my leather edges once because the coin ideas seemed like too much work. It did take a while, but it seemed to get the shape right without me having to worry about sanding levels. I noticed that the way the tool curves on the bottom of the edge seemed important even if the top was totally flat. Does the thickness of the tool matter as much as the shape when you are doing this?