On a recent science program I saw something called a “water saw”. It’s apparently an extremely high-pressure stream of water that can be used to cut through things such as steel. Is this real or is it theoretical,and if it’s real, who thought of it?
It’s real. It’s sometimes used to cut soft material like Styrofoam.
Often these are CNC machines and can be programmed to cut our quite intricate shapes - the water jet may be laden with abrasive particles to assist with the cutting.
Latitude Mfg. in Verona WI uses one of these to cut intricate inlays in tile and (I believe) stainless sheet goods. Pretty cool, I got to see it in action a few years ago. The water jet makes it easy to make cuts that are closed, i.e. they do not intersect an edge. Using traditional cutters, you would need to make a hole first then thread the cutting tool into that, this is hard in a design wehere the hole won’t fit.
Latitude makes the handles for Sub Zero Refrigerators and I was up there buying some custom ones for a project in Chicago.
There are two versions: regular waterjet cutters, which are used to cut foam, felt, or other soft materials, and abrasive waterjet cutters, which are used to cut plastics, metals, and other harder materials. These are becomeing quite common these days, as they can cut complex shapes without heating the material, and without the need to make expensive dies or stamps.
As noted, they’re generally called Water Jet Cutting, or sometomes more formally Water Jet Abrasive Machining Systems.
The core of the system is a huge set of pumps that progressively pressurizes water to somewhere around 25,000 to 50,000 psi. This water is piped to a CNC (Computer Numerical Controlled) head that forces that water out through a very tiny sapphire orifice, as I recall, less than .010".
The water alone will cut softer materials all by itself- some plastics, cloth, felt, cork, cardboard, even meat, fish and bread.
For harder materials, a small chute simply trickles a bit of an abrasive into the stream as it leaves the orifice. This is usually a fine-grained garnet stone, but other abrasives can be used depending on the material to be cut.
The benefits to waterjet cutting are the fact there’s no heat (as you’d have with laser or plasma-jet cutting) the material doesn’t have to be conductive (as with plasma again) and you can cut literally anything. Aluminum, plastic, carbon-fiber sheet, titanium, tool steel (without bothering to anneal it first) plywood, Lexan, stone, ceramics, mild steel, stainless steel, copper, brass, cast iron, glass, you name it.
And the computer control means it can cut damn near any 2D shape you can think of. The one I use on occasion (okay, I stand there and watch while the operator uses it 
) is quite simple. I bring in a drawing- it can be, and usually is, just a pencil outline on typing paper- he scans it, converts it to a Vector, converts that to the toolpath code for the CNC (a matter of a few keystrokes) then we test it by cutting a piece of thin, cheap aluminum scrap. I check the piece for the dimensions I need, we make any adjustments needed, he drops in the chunk of base metal, and pushes the button.
Ten minutes later I have 35 parts in my hand that would have taken me over an hour each to cut manually. It’s very useful.
So, if you could make the water pressure even faster you’d be able to do even more? Cool. The reason for my question is, I’ll confess, somewhat geekish, as I’m planning a book with a villian whose body is water (Hydro-Man, if you follow Marvel comics) . I heard about this thing and wanted to know if it was real, since it would make a badass weapon apparently. That and it’s just really cool sounding. Many thanks.
I’m pretty sure I have seen a documentary about the use of jets of water being used as a cutting device in medical procedures, I think it was used to cut out a diseased bit of liver. Am I imagining this?
What is the edge finish like on a piece of work from one of these machines?
-Somewhat rough. It tends to look “sandblasted”, which should come as no surprise. Depending on material, you will also have a “cut path” texture. If you’ve ever used an oxyacetylene torch and cut 1/2" or thicker steel, you;ll know what I’m talking about- the cut has vertical lines that might wave backward from the direction of cut.
In any case, depending on your application, it’s not usually a “ready to use” finish on metals. For my aluminum parts, I have the guy cut the pieces just a little large, and I’ll machine or sand it to size. For things like thin sheet, like punching a hole in a dash panel for a gauge, the finish is just fine. For stone and ceramic, the finish is actually probably perfect for mortar and grout adhesion. (The shop has some samples of 2" thick green granite cut into several interlocking shapes.)
-Well, higher pressure, yes. As it is, the 50K PSI and a bit of grit is enough to go through (I’m told) up to about five inches of damn near anything (stone, ceramic, steel, titanium, theoretically Depleted uranium, etc) and really, the only reason it can’t do more is the fact the water stream has started to spread, to turn from a stream to a spray by that point.
There are other unusual uses for water.
I’ve seen one of these used to cut ceramics before in the shop. I’ve been surprised at how loud they seem. I guess you think “water=soft” even when you know better.
At my university they used water-jet technology to cut the stones to make a half scale model of Stonehenge [=stonehenge]here](http://www.umr.edu/index.php?id=1917&no_cache=1&sword_list[)
Here are two links:
So when is Spinal Tap playing there?