A grinding machine uses an abrasive wheel as a cutting tool to shape or change the dimensions of a hard material. The type of materials that need grinding are usually metallic items such as tools and rods. These machines generally work by reducing the material through abrasion. Generally, the grain of the abrasive wheel chips away at the material, changing its shape or dimension.
Since the process of grinding metallic items often generates a great deal of heat, a coolant is often required to prevent the material and the machine from overheating. In high precision jobs, coolant may not be necessary. High precision grinding usually involves removing minute amounts of material, so very little heat is generated.
The basic parts that a user works with are typically the grinding machine's power driven wheel, the work-bed where the material is placed, and a fixture which guides and holds the material. The wheels, which can vary in size, are generally made from a manufactured abrasive such as silicone carbide or aluminum oxide. Depending on the job, the grinding head can move along the material that is being worked on or the grinding head can be set to stay in a fixed position and the material can be moved around it. The grinding head and work-bed positions can be controlled with features such as a vernier calibrated hand wheel, numerical control, or computer numerical control.
There are several types of grinders. This is necessary because all of the machines are not designed to perform the same types of jobs. For example, a belted grinder is a power-driven grinding machine used to process metals with the aid of coated abrasives. These machines are generally used for three applications: finishing, deburring, and stock removal.
Bench grinders are generally manually operated machines that have two wheels. Each wheel is likely to have different grain sizes, which are used for roughing and finishing. These machines are commonly used to shape tools in need of repair, such as tool bits. They are also used to shape metal that needs to be welded. Their grinding wheels may have to be switched when working with harder or softer materials.
The jig grinder is used for a variety of functions involving jigs, dies, and fixtures. These machines can be used to grind complex shapes and holes with a high degree of accuracy. Jig grinders typically operate using a removable, high-speed air spindle to rotate the grinding bits. Whether the speed of a jig grinding machine is fixed or adjustable varies from one machine to another.