Grinding Machines and Their Types

A grinding machine, also known as grinder, is a machine tool used for grinding. Grinding machines use an abrasive wheel as the cutting tool, with each grain of abrasive on the wheel’s surface cutting a small chip from the workpiece through shear deformation. Grinding is commonly done to finish workpieces that must show high surface quality (surface smoothness) as well as high accuracy of shape and dimension. More often than not, grinding is a finishing operation because it can accurately remove minuscule amounts of metal, at depths of approximately 0.25-0.50 mm. Despite this, grinding is a diverse field and is used in some applications to rapidly remove high volumes of metal.

A grinding machine consists of a bed with a fixture to hold the workpiece in place while guiding it and a power-driven grinding wheel spinning at the required speed. The spin speed is determined by the wheel’s diameter and the manufacturer rating. Depending on the configuration, the grinding head can travel across a fixed workpiece, or the grind head can remain fixed while the workpiece moves across it. The abrasion required to remove material from a work can generate a great deal of heat. To cool the workpiece so it does not overheat or exceed its tolerance, grinding machines utilize a coolant. In addition to keeping the machine cool, the coolant helps protect the machinist from burns.

While many types of grinding machines exist, the four most common are surface grinders, cylindrical grinders, centerless grinders, and cutter & tool grinders. A surface grinder consists of an abrasive wheel, a chuck (a device to hold the workpiece), and a rotary table. The chuck holds the material in place while the wheel and workpiece rotate to create a smooth finish. The most common surface grinders feature a grinding wheel rotating along the horizontal axis that cuts around the circumference of the grinding wheel. Surface grinders remove large amounts of material and grind flat surfaces with noted spiral grind marks. They can be used to make and sharpen metal stamping die sets, flat shear blades, fixture bases, and any flat and parallel surfaces. Surface grinders can be manually operated or have CNC (computer numerical control) controls.

Cylindrical grinders are used to shape the outside of a workpiece. They can be used on workpieces of many shapes and sizes as long as it can be rotated through a central axis. In this type of grinder, the workpiece and grinding wheel rotate simultaneously. Types of cylindrical grinders include outside diameter grinders, internal diameter grinders, and centerless grinders. Centerless grinders use two rotary wheels to secure the workpiece in place. This differs from a centered grinder, which uses a spindle. The speed of the wheels’ rotation controls the rate at which the machine removes materials.

Finally, a tool & cutter grinder utilizes a CNC machine tool with as many as five axes and multiple grinding wheels. Grinders of this type are primarily used for sharpening and production of milling cutters such as drills, end mills, and steptools, as well as a wide range of tools used throughout the woodworking and metal cutting industries. No matter the type of grinding machine you need, be sure you are getting parts from a trusted source.