When grinding, how to choose the right grinding wheel?

Machining

When grinding, how to choose the right grinding wheel?

There are many types of grinding wheels, and they have various sizes and shapes. The different abrasives, bond types, and manufacturing processes have their own applied field. If choosing the grinding wheel without properly evaluated, it is possible that it will directly affect the accuracy in machining, roughness, and production efficiency. Therefore, it is necessary to consider various conditions and situations to select a suitable grinding wheel and finally get satisfactory results.

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What is a grinding wheel?

A grinding wheel is a tool used for grinding. It is composed of coarse-grained abrasive compounds bonded together. After forming a solid circular object, grinding machining can be carried out on a grinding machine. The combination of grinding wheels mainly includes the abrasive, bonding agent, and pores, which have different functions. The abrasive can cut the workpiece, and the bonding agent is responsible for grasping the abrasive. Pores are for heat dissipation and chip evacuation, and the workpiece will change in size and shape due to grinding.

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How to choose the right grinding wheel?

There are many types of grinding wheels, including various sizes and shapes. There are different fields of applications according to different materials and performance just like cutting tools. If the selection is inappropriate, it will directly affect the machining accuracy, roughness, and manufacturing efficiency.

Abrasive selection

When choosing the abrasives, we can choose according to the workpiece and the heat treatment method. If the workpiece has high tensile strength, we can choose abrasives with high toughness, for workpieces with low hardness and high elongation can use brittle abrasives, etc., the following are the most commonly used grinding wheels:

Brown corundum grinding wheel: This type of abrasive has high hardness and toughness, and it is suitable for grinding metal workpieces with high tensile strength (carbon steel, alloy steel, etc.). This type of abrasive also has good grinding performance and wide adaptability. Coarse grinding that removes a large allowance is often widely used because of its low price. This type of abrasive has good grinding performance and wide adaptability and is often used to remove a large quantity of rough grinding as it is cheap.

White corundum grinding wheel: This kind of grinding wheel has higher hardness and lower toughness than brown corundum. When grinding, the abrasives are easily broken, so the heat generated is small. It is suitable for precision grinding of high-carbon steel, high-speed steel or thin-walled steel parts, etc., but the cost is higher than that of brown corundum.

Black silicon carbide grinding wheel: This kind of grinding wheel is brittle and sharp, and its hardness is higher than white corundum. It is suitable for grinding workpieces with low mechanical strength, such as cast iron, aluminum, or refractories.

Green silicon carbide grinding wheel: This kind of grinding wheel is more brittle than carbide black, with sharp abrasives and good thermal conductivity which is suitable for grinding hard and brittle materials such as hard alloy and optical glass, etc.

Chrome corundum grinding wheel: It is suitable for grinding tools, measuring tools, instruments, and other workpieces with high surface machining quality requirements.

Microcrystalline corundum grinding wheel: It is suitable for grinding stainless steel, bearing steel, etc., for forming grinding, plunge grinding, and mirror grinding.

Fused zirconia alumina grinding wheel: It is suitable for grinding austenitic stainless steel, titanium alloy, and heat-resistant alloy, etc., and is inclined to heavy-duty grinding.

Granularity

The granularity refers to the particle size of the abrasive, and the size is usually expressed by the particle size number. With a coarser granularity, the production efficiency is higher when grinding, but the surface of the workpiece will be rougher, while the finer granularity has better roughness but lower productivity. If the roughness requirements are met, coarse granular grinding wheels can be selected to maintain high production efficiency.

Hardness

Hardness refers to the difficulty of the grinding wheel abrasives falling off under the action of external force. According to the machining requirements of different workpieces, the grinding wheel will be divided into different hardness levels. If the selected grinding wheel is too hard, the dull abrasives will not easily fall off, resulting in blockage and grinding heat increased which will make the workpiece easy to burn, reducing efficiency and affecting the surface quality of the workpiece ultimately. If the grinding wheel selected is too soft, it will fall off when the abrasives are still sharp, increasing the wear of the grinding wheel, affecting the accuracy of the workpiece, and losing the correct shape. Therefore, when choosing the hardness of the grinding wheel, it is necessary to evaluate the contact area between the grinding wheel and the workpiece, the shape of the workpiece, the grinding method, the cooling method, or the type of bond types of the grinding wheel.

Bond types of selection

The most common bond types are ceramic bonds and resinoid bonds. The former is an inorganic bond, which has stable chemical properties, heat resistance, and good corrosion resistance. The grinding wheel using this bond will have high grinding efficiency and low wear which also can maintain the shape of the grinding wheel. Although it has a wide range of applications, the disadvantage is that it is brittle and cannot withstand severe vibration. The resinoid bond is an organic bond with high strength, elastically, low heat resistance, and good self-sharpening, moreover, it can make production simple and short process period, and its application range is second only to ceramic bonds.

Structure of selection

The structure refers to the percentage of the abrasives in the grinding wheel to the volume of the whole grinding wheel. The tighter the grinding wheel is, the better the surface of the workpiece can be ground. The looser the grinding wheel is, the larger the gap can ensure to hold the abrasives and avoid the blockage of the grinding wheel. The structure can be selected according to the material of the workpiece.

For example, when grinding soft metals, it is easy to block, therefore, the grinding wheel with a loose structure can be selected. When machining more precise grinding, the grinding wheel with a tight structure can be selected in order to ensure better roughness.

Conclusion

Before choosing a grinding wheel, it should be evaluated according to various conditions, such as abrasive, granularity, hardness, bond types, and structure, etc., plus different workpiece materials, grinding methods, and cooling methods. Many factors need to be considered, however, make full preparations before grinding, and even carry out a quality inspection with the assistance of smart tool holders during grinding, we believe the result will be satisfactory.

Main image photo by AdobeStock

Reference HonWay Materials

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