Tightline Productions shows us how sharpen a Matarelli style whip finish tool so it will cut thread. I looked high and low for a whip finish tool with a sharpened end like the one used in Tightline Productions fly tying videos, now I know why I couldn’t find one!
If you don’t already have one and you want to try this, you can pickup a Matarelli style whip finish tool here, for the grinding tools you are on your own!