A Water Jet Cutter From A Cheap Pressure Washer

We’ve become used to CNC mills and 3D printers becoming staples of our workshops, and thanks to the wonders of international trade even a modest laser cutter is not beyond the reach of most experimenters. But there is one tool that has so far evaded all but either commercial operations or the extremely well-heeled, the water cutter. These machines use a high-pressure water jet, usually carrying a stream of abrasive particles, to cut through the material placed beneath them. From our perspective they are interesting in that they can cut metal, something not normally possible with the laser cutters within our reach.

A water cutter is something you might think would be impossible for an experimenter to make for themself, but [Applied Science] is on hand to disprove that notion. He’s taken a cheap pressure washer, and modified it to produce a much higher water pressure for a water cutting head.

His very detailed description of the modifications makes for an extremely interesting watch, and we’ve placed the video below the break. The higher pressure is achieved by modifying the washer’s pressure on-off switch with a newly-machined sleeve and a stronger spring. The description of how the washer switch works is interesting in itself. Then we are treated to a complete teardown of a water cutting head, with abrasive feed, tungsten carbide tube, and ruby nozzle. This last component is surprisingly cheap. He then gives us a run-down of its design, particularly with respect to choosing the size of the orifices to match the pump. Finally we take a look at his abrasive feed system, and the plastic funnel he uses to keep water flow back out of his hopper.

For now the cutter is static, but his obvious next step is to bring it to some form of CNC table. If this project brings water cutting one step closer to the masses, we can’t wait!

We’ve featured more than one water jet cutter here in the past, but nothing at this low a budget. A group of students built one for about $5000, while there was a crowdfunding campaign for one at about $3500.

Thanks [varun s] for the tip.

66 thoughts on “A Water Jet Cutter From A Cheap Pressure Washer

      1. He only risks it if his fingers slip underneath the jet. You do get showered with water occasionally, but it’s low pressure.

        Popping back to the main thread, he’s using some of the same brands and parts that our real water jet uses. We use a .040 mixing tube, .014 ruby (or sapphire. Diamonds are also available). There is a metering disk to regulate sand flow (.220, or so). 55,000 psi water, and it uses perhaps 0.8 lbs/min of 80 grit garnet. Where as he’s going 1 ipm thru 1/8″ Al, that would be good for 3″ of mild steel on our little machine, if I recall correctly.

        Nice little proof-of-concept he’s done.

  1. Oh boy. I was doing research on power washers, and came across a Consumer Reports article that went on about how the red tip (highest pressure) can cause severe lacerations and the manufacturers should not be including it in consumer level washers. I can imagine how fast you could cut your finger off with this contraption.

    1. One of our workmates lost a finger only a few months ago while cleaning a heat exchanger with an industrial pressure washer. The consumer washers aren’t really too much lower in pressure (but much lower in volume).

      Though calling for them to be banned is stupid. There’s always reasons to want bigger better faster and higher power, even in the home. I can cut my finger off with a chainsaw too, but we don’t see calls for those to be banned.

      1. All hydraulic pumps (water or oil) are low or high volume rated. (As in: Engineered)
        All hydraulic systems need a pressure relief valve of some sort to prevent Hydro-Lock. or explosions.
        No such thing as a high pressure pump, just a pump the will not explode when the volume exceeds system maximums. (Called running pressure) If the pump volume exceeds bypass flow rates, heat is created, and all bets are off. And yes, for our purpose, liquids are not compressible. Lab nerds may not agree.. :)

      1. Sure it can. It can cut tempered glass so beautifully. It cuts straight in without effort the second it comes in contact with it.

        The result explodes but there’s no denying it cuts it.

  2. Just – no. If you are smart enough to build one on your own, maybe great. If you need help or inspiration, then just keep back.

    The ratio of will-hurt-you to looks-safe is higher than what most people ever encounter. While there are certainly items in the world that can injure – such as, but not limited to: chainsaws, table saws, nail guns, fire arms, high explosives, venomous snakes, brown recluse spiders, etc – this has a little stream of water that many will fail to properly of fear.

    I’d rank this with an open-air CO2 laser for stupid-human tricks.

    If there’s a need, find a company and let them do the water jet cutting for you. The result will be better and faster.

          1. Uhh ohh, infinite loop!

            The first use for water jets was actually cutting food, which is delicious.
            Instead of garnet they use sugar and cinnamon.

      1. Even though I’m glad [Ben] did and shared this, I think this equivalence is disingenuous. It’s running at much higher pressure (10x I think?) and with a more restrictive nozzle (converting more pressure to kinetic energy) AND abrasive in the stream. It is certainly more dangerous than it was before it was augmented.

          1. Which is not what most consumers have. But when you compare anything to commercial or industrial equipment the level of “safe” just becomes a meaningless word.

      2. Well, a regular pressure washer may only just be able to pierce your skin, but it has no garnet in there to help it do so. A water cutter will get into you in milliseconds.

      3. Well for starters, Ben is overdriving the pump, running at nearly 150% of what the washer was supposed to, that difference in pressure is pretty notable…
        Also, he’s not using the original fittings and connectors, if someone recreating this fails at that part – it’s gonna get nasty. While the fluid is not very compressible, the hoses do expand under pressure, so there is energy storage, and it’s not insignificant.

        That being said, if you use your brain and think about what you’re going to do before you try to do it, you should be reasonably safe. Just don’t treat it as harmless, because you will get hurt if do something dumb.

    1. “If there’s a need, find a company and let them do the water jet cutting for you. The result will be better and faster.”
      … dang.. does that mean I need to go back to cutting my fingers off with a regular hacksaw.. now where’s the hack in that…

      Get real.. this is a neat hack, and I learned a lot about water cutters in the process.. If I wanted to spend a few grand on a water cutter, I am more than capable of doing so, however if the zombie apocalypse occurs and all I have is a petrol generator and a pressure washer, then I might be able to fabra-coble together a portable zombie chop saw with this hack, so don’t dismiss it, you never know when the concept might come in handy,

    2. Of course the result of a commercial service is better and faster. But I don’t see the comparison with an open air high power laser: The range for dissipation of the water jet is much shorter than for a laser beam and the laser beam is invisible.

      1. The typical pressure washer places the outlet at the end of a long rod and has a valve that shuts off the flow when the user lets go. This encourages the user to place their hands very close and continues running.

        This is what a pinhole leak in a similarly pressurized system can do:


    3. Its against the natural order to protect idiots from themselves . Nature meant for them to be removed from the gene pool by their own stupidity prorecting them just dumbs down the general population. Besides your not my mom.

    1. Yes. But that doesn’t really do much for you if the pressure stays the same. It would give you a higher volumetric flow rate but would not really help you cut much faster though since the pressure would not increase and at the low pressures they are cutting at, that would not really help cut through material faster. What actually impacts the cutting action is dictated first by the pressure (if pressures are too low, nothing happens) and then by the flow rate. You can increase the flow rate once you hit a certain pressure but that typically is done so you can use more cutting heads at the same time (and is the reason why you can commercially buy 100 or 150 HP pumps).

      Think of it like current and voltage. If you only bumped up the voltage but the current remains very low, you would wind up with a Van de Graaff generator. Increasing both together starts to have a materially bigger effect than just increasing either one without also increasing the other.

    1. You can find high pressure water pumps on there now. Unlike 3d printing though, the issue with these type of devices are considerably harder to easily just fix or make work. Where do you put the spent abrasive? How do you get it out? It uses around 0.4 lbs per minute and because the pressures are so low, you can only cut very, very slowly. So you are talking about cutting for an hour or two just to cut one thing at an inch or less per minute of total cut depending on the material and thickness. So you cut one thing and wind up with 50 lbs of spent, wet abrasive (so it weighs even more because it is soaking wet). You not only need to buy 50 lbs of original garnet (and pay to ship it to you) but you also need to dispose of it. It also needs water and drain hookups and it’s going to be more expensive than a cheap 3d printer because of what it has to do. The motion platform need not be terribly rigid as the forces that it puts out are low but it has to withstand water (so corrosion resistance is a factor) and also absorb the impact of the water so you don’t cut through the bottom of the tank and spill hundreds of gallons of water everywhere. It’s also quite heavy because of so much water and uses a solid amount of power.

      Not saying it cannot be done and don’t get me wrong, I would make use of one if I had one at home; just don’t expect it to be as easy as you might expect.

  3. Now I’m wondering two things:
    1) can a hydraulic intensifier be had for “cheap”
    2) i wonder if such device would be able to use water in the first stage instead of oil…

    1. Define cheap and yes, but corrosion would be a considerable problem if you used an off the shelf unit originally designed to be used with oil but instead used purified water instead.

    2. I think a better question would be if you can abuse a commonrail diesel pump with water, as that can easily go 1000+bar just on it’s own. While not as cheap, they are plentiful and can be found in junkyards.
      They also tend to have a pulley no the input shaft, so you can easily mate it to a beefy asynchronous motor (or a suitable ICE :D)

      1. You would probably have to put some corrosion inhibitors into the water. There are water based hydraulic fluids for some special applications. But that means you have to use your working fluid in a closed cycle. Not impossible, but much more effort as you have to filter and purify it.

    1. But a laser cutter is useless once you try to do heat treated materials that you want to stay heat treated (unless you have a fancy oven to heat treat the part back to spec).
      Also, a cheap laser cutter can’t do ceramics or glass, this is where the DIY water jet would shine.

  4. I know what hydraulic injection injuries are… I’ll pass on this idea. One pinhole leak somewhere or a hose connector failure at an inopertune moment and you are in deep trouble.
    Basically the instruction for an ER doctor with injection injuries is: Start cutting. Keep cutting. Even further. No, deeper than that. Nope, deeper still. Especially in softer tissue high pressure water just keeps going, carrying dirt, debris and bacteria very deep into your flesh. It all has to be cut open and debrided to stop infection and even then there is a huge risk of losing limbs or life from infection and complications later on. Flushing out the wound is NOT enough.

    1. I get your concern, but I can give myself fatal septicaemia in many other weird and interesting ways.

      If you take suitable sensible precautions, you should be fine.

      Just because something is dangerous, doesn’t mean you shouldn’t do it, merely that you should asses the risk, and take suitable preventative measures to eliminate as much of that risk as possible.

      I spent my formative years fixing colour CRT devices and switch mode power supplies, both of which can kill you in an instant. For good measure I went rock and ice climbing at the weekend, and drove a sporty little hatchback. I suspect I, and probably everyone reading this, have come closer to our untimely demise on more occasions in various vehicles than I ever have while messing with 36kV, or dangling on a rope. However most peoples perception is that the car is safe, and High Tension electricals, and high places are for nutcases. It all depends on the risk you chose to expose yourself to, and your understanding of that risk.

      One of the most important things we do in this life, is learn to take, and asses risks, and I would suggest that while the risks here are very real, with a sensible approach, they can easily be brought to safe levels.

      1. That’s the operative phrase, “risk assessment” and the important question with something like this is the audience capable of making that assessment? One would normally says yes, but then there are the Darwin awards to prove that’s not a certainty.

        1. In my opinion your responsibility ends once you have made them aware of the risks.
          Once a person is aware of the risks it is their responsibility if they choose to take them. You probably don’t want to be limited by the least capable person in your area.
          Little Timmy was born and now you are not allowed to own knives until he is old enough to handle them safely.

  5. Too scary. I think I’ll spend the bucks to use the waterjet cutter at my local TechShop (the only thing they’re good for—I have better machines than they do for almost everything else).

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