Cutting Granite with Water Jets

A granite kitchen.
  • 1-100 hours
  • Advanced
  • 1-1,000,000

Cutting granite became a lot easier with the invention of the water jet cutter. Although the technique was around as long ago as 1852, when it was used in conjunction with steam for mining operations in California, it wasn’t until recently that the technique was perfected.

How Water Jet Cutting Works

A high-pressure water pump forces the water down into a diamond or jewel nozzle. The opening at the end of the nozzle can be as tiny as one-hundredth of an inch in diameter. The combination of the water being injected under high pressure and the narrowing of the tube nozzle forces the water to exit the nozzle with a force of 55,000 pounds per square inch.

For soft materials like wood and some metals this is enough; however, to cut an extremely tough or dense substance like granite, a supplemental aggregate must be added. This aggregate is usually made up of either garnet stone or aluminum oxide. Both of these aggregates are used because of their extreme hardness and their sharp crystalline facets make them perfect abrasives, even when they are broken down into a fine sand. The resulting width of a cut can be as narrow as four-hundredths of an inch wide (and down to three-thousandths of an inch when not using aggregates).

The Benefits

A granite island.

Water jet cutting machines provide many benefits over the traditional granite cutting saw. One of the benefits is that most of the cutting is done below water, thereby eliminated any airborne by-products such as dust. Also, there is no chance of heat damage to the granite or to the saw when using a water jet machine.

While a water jet cannot be operated by hand because of how large and heavy the machine is, it is run by a complex computer program instead. This program allows the machine to cut extremely intricate shapes into granite with perfect precision over and over again. The machine is so precise, in fact, that when cutting something like a granite tile out of a slab of stone, the edge that is cut is the finished edge.

This means there is no additional sanding or filing required; the cut will be perfectly straight and smooth immediately after it’s been cut. Furthermore, the pressure and length of time the jet sprays an area can be adjusted, which allows the saw to cut into the granite without cutting all the way through it. Utilizing this feature, the water jet can sculpt a piece three-dimensionally or simply etch something into the surface of the granite.

The Drawbacks

Granite in a kitchen.

Water jet cutters are very expensive machines with a single cutter, sometimes costing over one hundred thousand dollars. That price does not include the cost of operating the machine or the cost of the aggregate that would be needed to cut through granite. Yet, even if money were no issue, there are other drawbacks to these machines such as the training required to learn how to operate the machine properly, the large size of the machines and difficulty of finding a place to put them, and the length of time it takes to actually machine a piece of granite.