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.

29 thoughts on “Tiny Improvised Grinder/Saw Packs a Punch

      1. 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.

    1. 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.

    2. 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.

    1. Oh, I’m pretty sure his arm is not going to get pulled into that saw, and ripped off.

      His risk of being cut by the sharp edges of pins, boards, etc, is far greater. Plus there is the whole blister and soreness that comes with doing repetitive tasks. And there is the flying debris striking his hands as he cuts.

    2. Yeah, I’m with you too about gloves and power tools, but this hardly qualifies as such ^^U
      Limiting current to 2,5 amperes gives it plenty of power to cut, but if something got caught, it will stop immediately.
      I’m a lot more concerned about not having a motor guard, or for that matter, a disc guard (in case of disc breakage)
      Once I get the laser pieces, I’ll do it again, way better, still, cheaper than a dremel/cheapass copy.

      1. Yeah, it’s never a problem until you lose a finger.

        There’s a reason fences and push-sticks were invented. Add those, they’re not that complicated.

      1. Noo, I don’t work at a machine shop! (I have the machine tools at home, wich, by the way, I never use with gloves unless they are unpowered, and I also tie my long hair very tight). I work at an electronic engineering firm, and we don’t have much on the power tooling area… ^_^U

  1. 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.

    1. 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.

  2. 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…

    1. I already said I was VERY concerned about not having a disc guard.
      But the cutter itself it’s quite secure. With the trafo on top, it won’t move around at all. (rubber conductive matt underneath prevents that.

    1. 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.

      1. 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.

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