Grinding is an integral process of removing unwanted material from a casting or workpiece. In today’s industry, the grinding process is used on a broad range of ferrous and non-ferrous metals, and on non-metallic materials from rough snagging and dimensioning to the development of fine finishes. In most aspects, grinding is similar to milling, turning or other metal cutting operations. Importantly, the difference of grinding from these operations is what gives it a real value for a broad range of production processes. Instead of using a relatively small number of cutting edges per tool to remove material, a grinding wheel contains many thousands of hard and tough abrasive grains that move against the workpiece and cut away tiny chips. Because grinding is essentially a more gradual, less harsh method of machining a workpiece, a host of variables may be controlled with a far greater degree of precision.
In a foundry the grinding process is mainly used to accomplish stock removal. Stock removal or rough grinding, is an operation in which completed part tolerance and finish are secondary to getting the raw workpiece to an intermediate size or degree of finish. The most common types of stock removal in terms of grinding are rough snagging, swing frame grinding, portable grinding, cutting-off and steel conditioning. The primary objective of this type of grinding is maximum material removal in a minimum amount of time.
Because stock removal, in most instances, is rough grinding that brings the workpiece to approximate dimensions, most stock removal grinding is done offhand. This means, either the workpiece or grinder is handheld, and the quality and quantity of grinding are left to the skill and stamina of the operator.
Snagging is a type of stock removal most often used in foundries, to clean and dimension castings after they’ve been poured and have cooled. Gates and risers are removed, as well as stubs, fins, parting lines and accidental surface roughness. For castings small enough to be picked up and brought to the wheel, floor stand grinders are most commonly used, with the casting being hand held and cleaned as necessary.
Swing frame grinders are used on castings which are too large to be brought to the wheel. Rather, the entire grinder is suspended on a jig over the work area, and counter balanced in order for the operator to press the wheel into the workpiece.
Portable grinding is one of the most widely used kinds of stock removal in foundries. The grinder is powered by air, an electric motor or a flexible shaft. For heavy-duty jobs, such as cleaning a casting or removing a large weld bead, the wheels used and simply termed portable or hand program wheels. Raised hub wheels are used in most portable grinding jobs where the grinding requirements are not as severe. These wheels are also known as depressed centre wheels. They are often used to smooth down flat and curved surfaces for painting and finishing, to clean up weld lines, and to clean and smooth corners and joints.
Cutting-off is an abrasive application where the grinding wheel is used as a saw, cutting entirely through the workpiece instead of grinding its surface. In foundries, cut-off wheels are used to trim gates and risers from castings.
Mounted grinding wheels, more commonly known as mounted points are small grinding wheels with special shapes, mounted permanently on a steel mandrel. Mounted points are commonly used in foundries for cleaning and polishing difficult to reach spaces on the workpiece.
Grinding Techniques’ Andor range offers specifically developed and engineered grinding wheels to offer both high stock removal and optimum results when it comes to swing frame grinding and snagging.
With the Superflex hand operation cutting and grinding wheels you will easily find the right product to suit any grinding application. Apart from the Andor and Superflex range, Grinding Techniques also stock a wide variety of mounted points, tungsten carbide burrs and a range of coated abrasives inclusive of flap, Velcro and fibre discs and sanding belts.