Why You Need a Flat Bottom Counterbore Drill Bit
If you've ever tried to seat a bolt on a curved surface, you know why a flat bottom counterbore drill bit is such a lifesaver. Most standard drill bits come with a pointed tip—usually at a 118 or 135-degree angle—which is great for starting a hole in a flat piece of stock but absolutely useless when you need a perfectly flat "seat" for a fastener. If you use a regular bit to create a recess for a bolt head, the bolt is only going to touch the outer edges of that angled hole. It's unstable, it looks sloppy, and it can even lead to the material cracking under pressure. ...