Sharpening Drills Bits the Hard Way

Drill bits are so cheap that when one is too chowdered up to keep working, we generally just toss it out. So you might expect a video on sharpening drill bits to be somewhat irrelevant, but [This Old Tony] makes it work.

The reason this video is worth watching is not just that you get to learn how to sharpen your bits, although that’s an essential metalworker’s skill. Where [This Old Tony]’s video shines is by explaining why a drill bit is shaped the way it is, which he does by fabricating a rudimentary twist drill bit from scratch. Seeing how the flutes and the web are formed and how all the different angles interact to cut material and transport the swarf away is fascinating. And as a bonus, knowing what the angles do allows you to customize a grind for a special job.

[This Old Tony] may be just a guy messing around in his shop, but he’s got a wealth of machine shop knowledge and we always look forward to seeing what he’s working on, whether it’s a homemade fly cutter or a full-blown CNC machine.

27 thoughts on “Sharpening Drills Bits the Hard Way

  1. Wow I wish drill bits were cheap! (Well at least inexpensive)

    If anyone in Oz has a recommendation for bits that last more than two holes in mild steel let me know.

    Till then I’ll have to keep sharpening ….

    1. For bigger holes om steel, a C5 carbide annular cutter will allow faster cuts with coolant and correct feed rates.
      It is very common to see C2 carbides from asia (intended for wood/plastics), and even TiN coatings will rapidly wear unevenly.

      However, If you wisely use a good reamer after the cut cools, than the wear pattern of carbide tools won’t affect your work.

      This video is not the right way to maintain precision tooling, and you should drink a beer to forget the bad advice.
      ;-)
      Also, most HSS have a list of issues given it is usually just leftover bearing steel from an china factory.

        1. Unfortunately, precision milling carbide tools uses equipment not in most home shops.
          This 4-axis unit makes the fist cut on an end-mill (usually drill bits are tossed), and it is why you often see those flat facets on high-end hard carbide cutters.

          1. That’s really interesting! Thanks for sharing. :)

            A silicon carbide grinding wheel will grind tungsten carbide just fine. One might want to get some practice in on HSS before going with carbide because HSS is much cheaper.

    2. Use cutting oil and don’t run the bit so hot that it changes color. Don’t let it get so hot while grinding it that it changes color either. – When that happens the HSS gets annealed and loses its otherwise incredible strength.

      Cobalt HSS withstands more heat, but cobalt is up there with blood diamonds due to politics in Africa right now.

    3. I by no means have tried everything, but I’ve had much better results with the toolex cobalt drills from Gasweld than most hss drills. Going from a set of Frost hss drills to Toolex cobalt is a noticable difference. I’m not sure how their strength compares if your hand drilling and applying any sideways torque, I’m mostly using them with a mill.

  2. Buy quality bits, learn to sharpen them and your kids or grandchilds can inherit them. Better for the environment. Better for your wallet. AND the tools themself are often way better and will produce better results. This wisdom applies to almost everything btw…

    1. For those of us who aren’t full time machinists or have access to production shops, any suggestions on what company makes “quality” hss or carbide bits?

      (Answers of “my set from Company N lasted me 20 years” don’t count unless the company is still making quality bits)

      1. If you’re in the US you can find SKIL drill indexes at Lowes (my preference for affordable drill bits). Don’t bother with Dewalt, they are awful (well, the type that says “High Helix Angle”). I have used a set of Hitachi drill bits and I was pleased with their performance, but they don’t seem to be very common. I have found that drill bits sold at Fastenal (can’t recall the brand) are of good quality, and they have a good selection in the shop — if they don’t have what you want there they will order whatever you want, but their prices can be a bit high. Bright HSS bits are suitable for almost any work in non-hardened steel, don’t bother trying to find a set with a special coating. The advantages of surface treatments may be noticeable on CNC machines (longer life, less friction, etc…) but won’t make a bit of difference in a hand drill or a drill press.

        Anyway, learning about Surface speed and how to calculate the correct RPM for a given size drill in a given material will add to your drill bit’s longevity, as will coolant and cutting oil (depending on the material). I find a mild solution of dish detergent in water (or just plain water) to be more than suitable for HSS tools in mild steel, which is probably the most common combination anyway.

        I wouldn’t recommend carbide bits in anything less than a tight drill press. They are too brittle for hand held drills unless you have a steady hand.

  3. Purchase a high-quality sharpener, and don’t drill when the bit is dull! Set it into the “dull bit bin” and actually sharpen the thing.

    And keep moisture away.
    A rusty bit is a short-lived tool.

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