Precision grinding is usually the application of choice when a workpiece consisting of either ferrous or non-ferrous metal, plastic or rubber is to be finished to a tight tolerance with a high degree of surface finish. Popular grinding applications include external-and-internal cylindrical grinding, surface grinding, centreless and gear grinding, as well as tool and cutter grinding all used in various industries, like rolling steel mills, automotive and bearing industries, as well as cutlery, electronics, medical technology and tool production.
External cylindrical grinding is mostly used to grind parts with a cylindrical profile, it is used when the edge of a spinning workpiece which is rigidly supported, is required. With this application, it is essential that the workpiece is clamped with a chuck or held between two centres. Prior to the development of high-speed precision grinders and machining processes, workpieces requiring this application would have been roughed out on a lathe before being precision ground.
External cylindrical grinding is used in a number of processes ranging from, plain cylindrical, to special cylindrical where workpieces such as camshafts and crankshafts are produced within the Automotive aftermarket industry, and shafts up to five meters in length are produced within the Hydraulic cylinder industry.
With grinding wheels today being manufactured with Sintered Aluminium Oxide, achieving both roughening and finishing is possible with only one machine, where even workpieces that have been hardened, can be ground on an external cylindrical grinding machine.
In contrast to External cylindrical grinding, Internal cylindrical grinding is a process where the internal circumference of a cylindrical part is ground. Particularly popular in industries where jack hammers for the mining industry is ground, it is known as a process to enlarge and true, straight, tapered or form holes already machined, or hardened, into a workpiece requiring a high surface finish.
With Internal cylindrical grinding, it is of utmost importance that enough stock is left on the workpieces with long holes and thin walls, as the workpiece could get distorted during the heat treatment process. The type of material to be ground should be carefully considered when selecting grinding wheels, as material that is hardened might require a certain specification with a fine grain size.
Surface grinding on the other hand is often misunderstood, surface grinding is used to grind surfaces with a flat, contoured, or angular surface, therefore it is primarily used on workpieces requiring a flat surface, and when a specific tolerance and surface polish is required and not only for grinding any surface regardless of its shape. A typical application includes, manufacturing of industrial knives, where the grinding media for this application is available in wheels, segments and or cups-stones.
Another popular precision grinding application found in the aftermarket Tool and Cutter Grinding Industry, this is the sharpening of milling cutters, reamers, taps and drill bits. Although dry grinding applications are the most popular it makes grinding parts with no burn quite challenging. Selecting the correct type of abrasive grain, grit size, hardness, structure, and bonding system for this application remains crucial. Due to its friability, white aluminium oxide grain would be perfectly suited for these applications where workpieces that have been hardened needs to be ground with no burning to the workpiece
For further information contact Grinding Techniques on TEL: 011 271 6400 or email info@grindtech.com or visit www.grindtech.com
