I've been thinking about buying one of these but I don't know if they are just a gimmick. Also, if they genuinely work well how good do your bits need to be in the first place to be worth sharpening?

How to sharpen drill bits with a homemade tool for angle grinder House Republicans give GOP senators ultimatum over SAVE America Act Dolly Parton leaves fans emotional over her latest personal update ...

We may receive a commission on purchases made from links. You can tell a dull drill bit more or less immediately. If you're drilling wood, you'll likely see thin wisps of smoke as it starts to burn.