The Art of Mastering Machines

A Guide to Selecting an Abrasive for Waterjet Machining

One of the most fundamental considerations when selecting your water jet cutting abrasive for optimal profits and operation of include size and type. Your abrasive selection should start with assessing the material as well as the cutting specifications. A fabricator will consider the difficulty associated with cutting the material as well as the intended surface finish when deciding on a proper abrasive for the job. An abrasive part with the desired shape, rigidity, toughness, and density delivers superior results.

An abrasive may be natural or man-made, but it has to have the qualities below to suit your water cutting application:

Consider Hardness

There’s the need for waterjet cutters to have a fair compromise between speed and part wear. If you use a soft abrasive, nozzle life is prolonged, but cutting is slowed down. In case of a very hard abrasive, cutting speed is increased, but with rapid nozzle damage. In the end, cutting accuracy is compromised, downtime increased, and costs of frequent nozzle replacement become an issue. An abrasive that lies from 7 to 8 on the Mohs scale is ideal for a long lasting cutting tool and excellent working speeds.

Excellent Density

Mass multiplied by velocity is the function defining the key cutting power of a waterjet. Thus, an abrasive is great if it carries the most dense particle, which the water jet accelerates to optimal velocity. In the end, this achieves maximum cutting power. A compromise is important here as a too light abrasive is not forceful enough, while one that’s too heavy won’t achieve maximum velocity, draining the water stream of its full force. An abrasive of 4.0 specific gravity would work for good cutting power and optimal velocity.


How well the abrasive for water jet cutting performs is directly dependent on its toughness. If the material’s not tough enough, it comes apart in the focusing tube, unable to cut effectively for being too soft. Excessive toughness leads to rounding over the mixing process with the abrasive becoming too dull to cut effectively. An abrasive that’s tough enough for a measured breakdown rate is preferred to yield sharp cuts.

Partical Structure

There are numerous particle shapes for different abrasives, from beads, such as steel shots, and extremely sharp crystals for silicon carbide–an artificial product meant for high-tech application. Spherical particles may be a fabricator’s number one choice, considering that a sphere is the perfect means of carrying mass that’s projected in an extremely forceful water stream. Yet, when it comes to water jet machining, selecting the perfect particle shape for an abrasive must take into account the need for acceleration, durability, and cutting effectiveness.

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