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Posted on Aug 10, 20208
Modern surface grinding wheels can be regarded as rotating cutting tools with an infinite number of cutting edges. The latter is formed by small fragments or crystals of hard material and embedded in a softer matrix or bond. Compared with a machine tool that uses a single-point tool, a large number of cutting points acting at one time will result in a very small load at each point, so the tendency of the grinding wheel to bounce off the workpiece is much smaller.
Here the same principle applies, but it is modified due to slower abrasion and usually heavier load. These conditions were found to be better for removing very small amounts of metals under strict control. Surface grinding wheels come in various sizes and types of abrasive grains, as well as bonds used to increase the grinding performance of specific sizes. In this article, we will tell you what you should pay attention to when choosing a new grinding wheel for a surface grinder.
The type of material will affect the choice of your surface grinding wheel, particle size, and grade of the abrasive. Alumina type abrasives are best for grinding high-strength materials such as steel and ferritic cast iron. In harder steels and applications with larger contact arcs, the more brittle alumina type is preferred. Low tensile strength materials and non-metallic materials are most effectively ground or cut with abrasive silicon carbide. The hardness of the material determines the degree of traction the abrasive can obtain. Therefore, it is necessary to use a fine-grained grinding wheel to grind hard materials, and it is best to use a medium- and coarse-grained grinding wheel to grind soft materials. For the most effective operation, the grade must be adjusted to suit the hardness of the material.
Surface grinding wheel specifications are also regarded as super grinding wheels. In addition, you may want to know that various specifications determine the application of a particular model. Let us discuss the different parameters one by one!
• Type Of Abrasive
Two types of surface grinding wheels are used in industrial applications. One of them is silicon carbide, a very sharp and very hard abrasive. However, its use as an abrasive is limited to some extent by its brittleness. Silicon carbide is used for grinding materials with low tensile strength, such as gray cast iron, cold iron, bronze, aluminum, copper, brass, and non-metallic materials. A special form of green silicon carbide is used for grinding tools with tungsten carbide. Another most common abrasive is alumina. It is softer than silicon carbide but much harder. It is used for grinding high tensile strength materials such as alloy steel, annealed malleable iron, and strong bronze. There is another form of alumina, which is white, as opposed to the normal brown variety. Compared with conventional alumina, this white alumina is more prone to cracking, thus the surface grinding wheel provides more and sharper cutting edges to the workpiece. When grinding hardened tool steel or for grinding in general tool rooms, white alumina grinding wheels should be selected.
• Grit size
The size of the grit also depends on the size of the diamond and the grain diameter. For finer grains, finishing is good, while for finer grains, finishing on the end face is poor. Generally, coarse surface grinding wheels are used to quickly remove material. Use fine grinding wheels when surface treatments are considered important. Coarse wheels can be used for soft materials, but hard and brittle materials should usually be fine gravel.
• Type of bond and bond strength
These are defined by several factors including degree, strength, and hardness. It should be mentioned that the hardness can handle the material that binds/holds abrasive particles. For crystal grains with harder bonding, the service life of the grinding wheel is longer. But the clarity of the final product is lower, and vice versa. The bonding material holds the abrasive particles in the form of surface grinding wheels. When these particles become blunt or completely ruptured, the bonding material will release the blunt particles, exposing new sharp particles to continue working. This effect occurs because the sand particles become dull and the grinding pressure increases. The four main types of bonding are vitrification, shellac, resin, and rubber.
• Degree of concentration
It defines the content ratio of diamond to CBN abrasive particles in the abrasive layer. The higher the concentration, the greater the number of grains. For lower concentrations, there are fewer abrasive particles. The grade is a measure of the "holding power" of abrasive grains, which determines the hardness or softness of the grinding wheel. Most manufacturers use letters to indicate the grade of the wheel. Although the standard is different because the grade is not an accurate value, the grade letter usually increases the hardness from E to Z. Later in this article, we will discuss choosing the right wheel grade for a specific grinding application, but it is generally recommended to use hard wheels for soft materials and soft wheels for hard materials.
On a horizontal spindle surface grinder, the flat edge of the surface grinding wheel is in contact with the workpiece. The vertical spindle grinder uses the end face of the grinding wheel as a plane. These ensure rapid material removal and provide high precision. The disc grinder or double disc grinder has a larger contact area between the disc and the workpiece and can place vertical and horizontal spindles at the same time.
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The surface grinding wheel is composed of alumina, silicon carbide, diamond, and cubic boron nitride (CBN). The most commonly preferred and desired is alumina. For diamond and CBN, they are made of cheaper materials and then surrounded by a layer of diamond or CBN. The grinding wheel composed of diamond and cubic boron nitride is very hard in nature and can be used to economically grind ceramics, carbides, and other materials. Similarly, the wheels can also be grounded via diamond and CBN. The surface of the grinding wheel is maintained with abrasives that can be installed on the workbench or in the wheel head so that they can be reused.
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You can find many surface grinding wheel suppliers on our site that are suitable for gray cast iron processing. Just head to our product section or check out our search function to find hundreds of manufacturers in our product database. If you want to learn more about gray cast iron related questions and applications make sure to check out our other blog entries.
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