Tiny Improvised Grinder/Saw Packs a Punch

They say necessity is the mother of invention. Sometimes the necessity is simply avoidance of unpleasant tasks such as cutting down 3500 header pins by hand. [Nixieguy] and his coworkers were faced with 50 prototype boards bearing 70 overly long pins apiece. He saved them from cutting them all down by hand by making a tiny improvised circular saw/grinder.

[Nixieguy] started by laser-cutting a combination tool holder and grinding platform. His laser failed before he could fashion a guard to keep the pin bits out of the motor or cut all the pieces he had in mind. The grinder is made from a 10A brushless RC motor, a motor driver, and a servo tester. [Nixieguy] machined an adapter to connect the disc to the shaft.

The transformer is there to hold the thing down during use since it’s so lightweight. He’s wearing two pairs of gloves because the pin cuttings were hot enough to sear skin. [Nixieguy] is planning on a complete redesign including a motor guard and the ability to adjust the depth. Maybe he can turn it into a chainsaw, maybe not.


  1. Rich says:

    A $20 Dremel from the hardware store would do that too

    • Voltatek says:

      Well… If you want something that takes less space I think it’s a great idea. And also much less heavier

      • Nova says:

        You do realize it affixed to that giant piece of perspex so the wires don’t get damaged from being moved around, right?

        It’s actually much larger than a dremel but I’d imagine where it shines is there is a board-guide for perfectly flush cuts.

        I myself suffer from wandering-dremel-syndrome occasionally. So it has it’s uses.

    • yetihehe says:

      If I had laser cutter and all elements for this, designing this and cutting would be much faster than going to nearest hardware store and back. Also for dremel, you STILL have to make some assembly to cut the pins, otherwise it’s back to cutting pins one by one.

    • JRDM says:

      Eh, Dremels are not always the best form factor though, and even if you disassemble it for parts, not necessarily as good as this. I’ve not seen a Dremel that cheap, but it turns out there is a cordless 4.8V one for $25. This guy has an brushless motor with adjustable speed control, a roughly equivalent Dremel is maybe $80, and Dremels have brushed DC motors.

  2. sqelch says:

    awesome saw

  3. Gizmos says:

    I saw what you did there.

  4. Wyatt says:

    maybe its just me, but i have never ever used gloves around power tools. its just not safe.

  5. echodelta says:

    Will the rough ends of those pins scratch the receiving end’s plating when inserted? All pins are touched with the mating surface at a very tiny place and fail in time. Peterson pins are worst of all, 2 curved surfaces meeting at right angles. A theoretical point. I want triple redundancy.

    • Smorges Borges says:

      Good catch. The easy part is cutting those pins. The real work is in deburring! Oh the humanity!

      There’s also some minor concerns about lack of plating on the cut ends. But that’s nothin compared to the probable burrs.

  6. Thinkerer says:

    Forget the gloves – did you really just make a poorly secured circular saw turning at ridiculous speeds and no guards. I’ve got a lovely scar on my finger from when Dremel used to include a tiny circular saw blade (about the size of a dime) with its kits. I didn’t quite lose the digit…

  7. What caused the laser tube to break? Are you guys using a chiller for the water?

    • nixieguy says:

      Just stupid overconfidence on my part. (it’s my personal laser, I have it at home, not at work).
      I have been postponing to build a flow sensor for the refrigeration, and well, the one day you still haven’t built it, and you forget to turn on the pump… (cries some manly tears). I already ordered new parts and won’t be installing them, until the flow sensor is done.

      • JRDM says:

        I don’t have a separate cooler (one is built into the machine), but my exhaust fan is on the same power strip as the laser machine, and I turn on the power strip.

  8. Biomed says:


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