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Choosing the Right Grit Size for Waterjet Cutting

July 21, 2016MainPathNewsComments Off on Choosing the Right Grit Size for Waterjet Cutting


Although pure waterjet solutions are still used to cut soft materials (like paper and food), most manufacturing companies use abrasive waterjets to shape parts and components. In an abrasive waterjet system, the efficiency of the cut is about more than just hitting material with pressurized water — it’s also about selecting the correct abrasive, designed to cut through the material as cleanly as possible.

While garnet is the most common choice for waterjet grit — providing the hardness needed for clean, powerful cuts in even the most intricate of designs — this abrasive comes with flexibility, in regards to the grit size. Depending on what you’re cutting, the types of cut you’re making, and the intricacy of each cut; you have a crucial decision to make before you start the waterjet process. A larger grit won’t produce the same results as a smaller grit.

Choosing the right size grit for your waterjet project can minimize the consumption of abrasives, reduce unnecessary costs, and maximize productivity on the manufacturing floor.

The Factors Involved in Choosing Grit Size

Commonly, fabricators will have a selection of “mesh” grades they can choose from, when selecting the perfect abrasive (or grit) for a waterjet project. Each “mesh” grade represents a different grit size — and although they might not dictate the exact dimensions of each particle, they do give some insight into the general distribution of grit size.

There are three mesh grades that commonly appear on the waterjet market. These include:

  • 50-60 mesh — This covers larger sized particles, and tends to be for rougher grit applications.
  • 50-80 mesh — The common standard, known as “moderate” grit.
  • 100-220 mesh — The smallest grit size, for the finest possible particles.

Of these options, the 80 mesh solution is the most popular, for the majority of “general” projects.

How Grit Size Determines Your Project Results

Knowing the grit sizes available is one thing, but understanding how those grit sizes affect your project is another matter. Typically, the bigger your grit size, the rougher the cut will be. Smaller grits are for finer, more precise details — which means that your ideal abrasive will depend on what you’re trying to achieve in the machining process.

The grit size impacts a variety of factors, including:

  • Expenditure — While the cost of the materials for your project might not be the most important factor, it’s worth thinking about when choosing grit. Smaller mesh batches are generally much more expensive than larger grits; so, depending on the mesh you’re looking to use, your project could become costlier.
  • Speed and efficiency — The larger the grit size, the faster the cutting process will be. This means that a 50 mesh will often blast through materials faster than an 80 mesh; but it may also mean that you have to compromise on other things — such as surface finish.
  • Surface finish — If you are jetting with the hope to avoid secondary finishing procedures, the grit size you use is essential. Smaller grit will always lead to a finer, cleaner finish than larger grit. This means that a polished surface aesthetic requires a far smaller grit size.

Problems with Choosing the Wrong Grit Size

While it may seem simpler to choose an 80 mesh because it’s most popular, or stick to the least expensive grit you can find, selecting the right abrasive for your particular project is essential to achieving the results you want. The wrong abrasive can not only damage your components, or waste materials; it may also damage your waterjet machine by clogging the nozzles, and delaying productivity.  

Clogs can easily occur in waterjet machines, as a result of too much abrasive, or a mesh size that’s too large for a specific orifice diameter. Regardless of which grit size you choose, make sure that it not only suits your project, but the other parts of your machine too. Always use the correct nozzle/orifice combination, and select the proper orifice for the grit size you need.

Waterjet Abrasives and Cutting Performance

Grit size will not be exclusively responsible for your waterjet cutting experience — pressure settings, nozzle sizes, and orifices must all be considered, as well — but it does play a crucial role. Tailoring your grit size to your specific project will help you to get the best results possible, while structuring each cut in a way ideal for streamlining workflow. Choosing the appropriate grit size is essential to getting the perfect results you need, for a cost-effective and efficient fabricating process.

Which are your preferred grit sizes, and why do you like using them? Have you found that specific grit sizes work best for certain projects? Let us know in the comments below!

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