The process of grinding is the operation of removing excess material from metal parts by a grinding wheel made of hard abrasives. The following operations are generally performed in a grinding machine.
- Cylindrical grinding
- Taper grinding
- Gear grinding
- Thread grinding
Cylindrical grinding is performed by mounting and rotating the work between centres in a cylindrical grinding machine. The work is fed longitudinally against the rotating grinding wheel to perform grinding. The upper table of the grinding machine is set at 0° during the operation.
Taper grinding on long workpieces can be done by swiveling the upper table. If the workpiece is short, the wheelhead may be swiveled to the taper angle. Another method of grinding external taper is to true the face of the grinding wheel by a diamond tool dresser to the required angle. In this case, the table and the wheelhead are not swiveled.
The teeth of gears are ground accurately on gear grinding machines for their shape. Gear grinding is done by the generating process or by using a form grinding wheel.
The generating process makes use of two saucer shaped grinding wheels. These wheels are used to grind two faces of successive teeth.
The forming process makes use of formed wheels to grind a tooth at a time. This is a very precise method of performing gear grinding.
Thread grinding machines are used to grind threads accurately. The grinding wheel itself is shaped to the thread profile. These formed grinding wheels have one or multi threads on them.
Wet Grinding and Dry Grinding
Wet grinding – The method of spreading a good quantity of coolant over the work surface and wheel faces during grinding is known as ‘wet grinding’. Soda water is used as a coolant. The process of grinding generates high amount of heat generally about 2000°C. Various properties of the work material change due to the heat. In order to reduce the heat generated during grinding, coolant is used. Wet grinding promotes long wheel life and better look of the ground surface. Coolant is pumped from the tank through pipelines.
Dry grinding – Dry grinding is the method of doing grinding operation without applying coolant. Dry grinding produces undesirable effects on work surfaces. It leads to burring & discoloration of work surfaces.The cutting edges of the grinding wheel lose their cutting capacity. So, dry grinding should better be avoided.