Machining Without Machines

It’s a luxury to be able to access a modern machine shop, complete with its array of lathes, mills, and presses. These tools are expensive though, and take up a lot of space, so if you want to be able to machine hard or thick metals without an incredible amount of overhead you’ll need a different solution. Luckily you can bypass the machines in some situations and use electricity to do the machining directly.

This project makes use of a process known as electrochemical machining and works on the principle that electricity passed through an electrolyte solution will erode the metal that it comes in contact with. With a well-designed setup, this can be used to precisely machine metal in various ways. For [bob]’s use this was pretty straightforward, since he needed to enlarge an existing hole in a piece of plate steel, so he forced electrolyte through this hole while applying around half an amp of current in order to make this precise “cut” in the metal, avoiding the use of an expensive drill press.

There are some downsides to the use of this process as [bob] notes in his build, namely that any piece of the working material that comes in contact with the electrolyte will be eroded to some extent. This can be mitigated with good design but can easily become impractical. It’s still a good way to avoid the expense of some expensive machining equipment, though, and similar processes can be used for other types of machine work as well.

22 thoughts on “Machining Without Machines

    1. … but much higher chance of the tooling coming out of the drill column because the taper lets loose..

      Been there.. it’s not a fun experience to have a live tool tearing across the room..

      (20 years experience)

  1. We had an old machine at one of my jobs – from the 50’s I think. It used a large spool of what looked like #22/#24 copper wire that was fed through a steel plate using a cog to control the pattern. When they fed current through it, it could cut up to 6 inches thick of steel, slowly of course – but it worked. I think this is called electrical discharge machining (WEDM), apparently you can cut up to 11 inches or more using this technique. I always thought this was pretty freaky. It their case they would stack a bunch of steel plate to make a small run of a new design.

    1. EDM removes material by burning it with an electric arc. ECM is more like circuit board etching taken to a higher level. With ECM, you can etch whole panels in a single operation, rather than needing an electrode for each hole.

  2. ECM has been the way that the 3D printed gun community got around making a rifled firearm barrel out of standard hydraulic tubing. 3D print the tools, holders and the rest that you need and go from there. The primary guy on this is Ivan the Troll (his online handle) and the fast few days he mentioned that a newer and easier procedure and tooling is coming out in the near future without quite so much finicky bits. Article on the current, soon to be replaced process at

      1. I’m not seeing the irony. Are you saying that it’s ironic because to make a gun, which we can legally do in the USA, you have to order materials from a place that doesn’t allow its citizens to make guns? I’m sure you could get the materials in the USA as well. There’s no irony in materials being less expensive in countries with a lower standard of living. Or am I missing something?

        1. Well, it’s ironic in many ways. That is one of them.

          The idea of a “FUGC” weapon you can make yourself covertly falls on its face when you have to obtain specialty parts through mail, which a regular person would never need for anything, such as a specific length of a very specific hydraulic tubing. The whole thing is still a house of cards that comes down the instant the authorities decide enough is enough.

    1. Wow. Three in a row. The process described in the rifling project was EDM (electric discharge machining). It is a completely different process from electrochemical machining. ECM is more like printed circuit board etching, but instead of a pasive acid etch, the work piece becomes the anode in an electroplating system. It uses much of the same technology used for PCB fabrication.

  3. You can actually achieve some pretty scary accuracy with ECM, even something like threads or barrel rifling, provided your jig is up to the task. Warning from someone who has done it:

    Be extremely careful when ECM’ing stainless steel (or anything else containing chromium). Your sediment and deposits will be INSANELY toxic. Best done with a dedicated setup, where you have a sump or tray you can remove to responsibly dispose of chromium, away from people, pets, or groundwater.

    1. The toxicity of chromium (ions, not chromium metal) depends on the oxidation state of the ions. The most common states are +6 (found in chromate and dichromate compounds) and +3. I have not done ECM but I suspect that the +3 form (usually green) would be the product of ECM, as it is the more stable form…and it is also far less toxic than the +6 form (orange or yellow).

      From Wikipedia’s entry for chromium: While chromium metal and Cr(III) ions are not considered toxic, hexavalent chromium, Cr(VI), is both toxic and carcinogenic. Abandoned chromium production sites often require environmental cleanup.

  4. You have to be careful and provide good ventilation, because electrolysis of salt water produces both hydrogen and chlorine gases.

    The downside of erosion occurring on a whole workpiece can be mitigated to some extent by masking with appropriate paint or other impermeable finishes, although some undercutting will occur.

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