Hardware Store CNC Machine is Remarkably Precise

A vise, a hacksaw and file, some wrenches – the fanciest tools [HomoFaciens] uses while building his DIY hardware store CNC machine (YouTube link) are a drill press and some taps. And the bill of materials for this surprisingly precise build is similarly modest: the X- and Y-axes ride on cheap bearings that roll on steel tube stock and aluminum angles; drives are threaded rods with homemade encoders and powered by small brushed DC gear motors; and the base plate appears to be a scrap of ping-pong table. The whole thing is controlled by an Arduino and four H-bridges.

The first accuracy tests using a ball point pen for tooling are quite impressive. [HomoFaciens] was able to draw concentric circles eyeball-accurate to within a few tenths of a millimeter, and was able to show good repeatability in returning to a point from both directions on both the X- and Y-axis. After the pen tests, he shows off a couple of other hardware store tooling options for the Z-axis – a Proxxon rotary tool with a burr for engraving glass; a soldering iron for cutting styrofoam; and a mini-router that works well enough to cut some acrylic gears.

We’re impressed by this build, which demonstrates that you don’t need a fancy shop to build a CNC machine. If you’re getting the itch to jump into the shallow end of the CNC pool, check out some of the builds we’ve featured before, like this PVC CNC machine, or this $250 build.

[Thanks, ThunderSqueak]

20 thoughts on “Hardware Store CNC Machine is Remarkably Precise

  1. While a very cool build, the threaded rods will wear out quite quickly, so that will eventually ruin the repeatability and finally the whole machine. But hey, they are cheap to replace.

    1. Excellent technique, but threading a threaded rod over the lead screw won’t last. Why not nuts on either side and positioned to minimize thread lash. (Welding or jb weld would last longer than the threaded rods.)

    2. He could have opted for stainless threaded rods, they are more sturdy and would also last longer. Although I’m more doubtful about the bolts they run through. There again stainless would be better. But it’s harder to tap stainless though.

      Still nothing but respect though, to make this with cheap materials and mainly handtools and have it work that well is awesome.

      Incidentally, In my area stainless rods are not that much more expensive than regular ones, whereas stainless bolts are significantly more expensive than regular ones, oddly enough. It seems having heads on them increases the price a good deal..
      After checking it seems they use a rod that is then forged into having a head to make bolts, sometimes using several steps to get to the hex shape.

        1. So, you lubricate, or use stainless rods with hardened steel bolts.
          You should not all take it too seriously, there are plenty of stainless surfaces that rub all the time and that are fine for many years in my experience.

          Now aluminium, sure, that;s another matter – if you pardon the pun.

    3. Yes, cheap is the opposite of durable…
      Considering the low power motors (the machine moves just 3mm per second), the abrasion won’t be that much (I guess). I won’t run of used motor oil, thus there is always some lubricant handy. This machine is of course not for mass production. It was created to improve the build quality of my robots (www.RoboSpatium.de). Sometime I will do an upgrade with stronger drives (maybe stepper motors) and I have also an even cheaper machine in mind. I need more hors per day…

      1. That’s why I mentioned that in my experience stainless rods are not that much more than steel ones, so it’s doable in terms of price. But to be honest I’m clearly not too skilled at making hardware and I am aware that you and others might well know better, so I leave you to judge what’s best.

    1. It’s in the youtube description, but nevertheless it’s good to have it posted as a standalone link and Dan should have thought of that.
      So good post RoboMonkey. Completes the article.

  2. Precise? Seriously?
    Motor lead-screw couplings are plastic tubing.
    The only thing preventing the cutting lifting under load is the lead screw on the Y-axis. There are no bearings running on the underside of those tubes to hold it down.
    Rotary encoder with only 8-hand cut segments.
    It is impressive work with limited tools, but let’s stay real here. Commendable effort it is, precise it will never be.

    1. Did you see the test runs on paper, and acrylic, and glass engraving, and with an aluminium sheet?
      Clearly not if you say it’s not precise.
      I’ve seen efforts with parts ten times more refined and expensive and failing to have any precision, and yet here it does work. The reason for that from my guess is that it’s about knowing what works and what the critical areas are for achieving precision.. But that’s just a guess.

    2. …don’t underrate gravity. Another thing to be considered is the low speed of the machine, so the router is not lifted during operation. 8 “gears” and 8 “gaps” with 2 photo sensors result in 64 steps per revolution. With the 6mm rod, the axes move 1mm per revolution, thus there is an arithmetical movement of 0.016mm per step – not so bad. The precision is higher than cutting shapes by hand. That’s what it was made for.

      1. It belongs there because those rods move the axes. The overshooting during movement is no more than 2 steps at the rotary encoder which is 0.032mm in theory (remember the low speed). Caused by the flexible rubber tubes there is in fact some more overshooting at the motor side, but that doesn’t matter. It might become a more serious matter when using more powerful motors. The rubber tube is needed because of the low build quality when using all those simple tools for making a CNC machine. Having an attachment with (almost) no clearance on both ends, the (cheap, somehow buckled) rods would be jamming. With torsion of the rubber tubes under load, the error would be more than 0.032mm when mounting the sensor disc on the motor side.

  3. Dan, I’d love to see this CNC machine in action, I’m always fascinated with these types of equipment. My brother loves to make furniture and other types of woodworking things. He’d love to get a CNC machine, but I don’t know if he’s ready yet.

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