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A concrete grinder can come in many configurations, the most common being a hand-held Angle grinder, but it may be a specialized tool for countertops or worktops. There are also purpose-built floor grinders that are used for grinding and polishing marble, granite and concrete. Machines that grind concrete floors are usually made to handle much more stress and will have more power to drive the unit as concrete has a much higher sliding friction than marble or granite which is also worked wet, therefore with less friction. In fact some types of marble will spark when it is ground dry, causing deep damage to the marble surface.
All concrete grinders use some sort of abrasive to grind or polish such as diamond tools or Silicon carbide. The diamond tools used for grinding most commonly are diamond grinding cup wheels, and for polishing are usually diamond polishing pads. The use of diamond tooling is the most common type of abrasive used under concrete grinders and come in many grits that range from 6 grit to the high thousands, although 1800 grit is considered by the insurance industry as the highest shine to apply to a floor surface.
Concrete is usually ground dry for convenience, because it can be done with fewer people than wet grinding, although a HEPA filter-equipped vacuum is needed to capture the fine dust produced. Of course concrete can also be ground wet in which case no vacuum is used. Fine concrete dust contains silica which is very harmful to the lungs and can lead to silicosis so all effort should be made to avoid breathing concrete dust. For green building methods many regulators LEED's have seen the benefit of using concrete grinders that are designed to finish concrete to a very stable wear surface, that can safely be used for many years as a floor or tabletop surface . These machines are usually powered by higher electrical power such as 220 volts or higher as they require motor power larger than 110 volts can supply. Some machine are powered by LP gas such as used on forklifts so that they can be run in well ventilated areas without a power cord, but these machines usually have fewer features that a fully electric unit. Variable speed is one good feature only available on all electric versions, that allows for slowing down of the grinding speed to keep the tooling in contact with the floor.
The picture on the right is an example of a concrete floor grinder. This is a three-head planetary grinder, which has a three-phase motor and will run on single or three phase input power.