Centerless grinding accomplishes its tasks with the desired consistency but the process is done according to material shape and size to achieve that accurate precision in end operation.
Centerless grinding, commonly associated with “black magic”, is done through continuous material removal without the need to put a part of a workpiece on a fixture or place it on centers – that’s why it’s called “centerless”. Bars, axles, camshafts, etc. – all are inspired by centerless grinding. It grinds the surface of a turned round bar of material. The grinding machine consists of three “cylinders” including the grinding wheel, the regulating wheel, and a workpiece.
The artistic turning of wheels grinds the part shape to its perfect roundness, straightness, and specified diameter tolerance. But unlike any other machining operations that require one, two or few cutting edges, grinding wheels used in this kind of operation use thousands of abrasive grains constantly reapplied in the operation.
Types of Centerless Grinding
- For round bars and parts, through-feed centerless grinding is used. Typically applicable in the process are long bars (e.g. six to twelve feet long and more). It feeds into the regulating wheel and the grinding wheel. It enters the other side and flies out of the opposite side. The bar is pulled by the regulating wheel past the grinding wheel. Through-feed does not require any separate feed mechanism but it can only be applied on parts that have a simple cylindrical shape such as pistons, tubes, piston pins and bars.
- There is a work blade used in supporting the workpiece or the bar and holding it at the correct height just above the centerline of regulating and grinding wheels. This process is critical to the diameter tolerance and roundness of the bar. But the good thing is, both wheels held a consistent gap between them to control the bar’s shape. External feeding is not required in this process.
- For relatively complex shapes like camshafts and gear shafts, in-feed centerless grinding is used. The workpiece is loaded into the regulating wheel and the regulating wheel moved into place. Due to the complexity of part shapes, there is a need for the grinding wheel to grind them accurately, preventing it from being fed axially through the machine. The workpiece is held in a stationary position and the grinding wheel is being fed into the workpiece at specified depth and location.
- With a three-part positioning method, small diameters are even ground since they are entirely supported through their grind length. Smallest parts are ground extremely due to the kind of support it had.
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