216 / Bonded Abrasives www.youtube.com/NortonAbrasivesEMEA BONDED ABRASIVES PRODUCT SELECTION A grinding wheel is a precision tool with thousands of cutting points. It consists of abrasive grains held in a matrix of bond and separated by pores. The abrasive grains are the cutting points while the purpose of the bond is to hold the individual grains together. The pores (hollow spaces between adjacent abrasive grains and the bond) serve to provide clearance for coolant penetration and metal chips removed in the grinding process. When the wheel is rotated at grinding speed and applied to the workpiece, the abrasive grains cut the material that is being ground, removing the material in small chips. Under the action of the forces imposed during grinding, the abrasive cutting points are worn flat, resulting in the points becoming blunt. This causes an increase in friction, and a build-up of heat. The increase in grinding forces causes either the abrasive to fracture, exposing new cutting edges, or fractures the bond bridges holding the abrasive grains. In the latter case fresh abrasive grains are exposed to cut the workpiece. In normal vitrified grinding applications, the wheel has to be dressed. By varying the properties of the abrasive, the type of bond, the make-up of the wheel, it is possible to produce grinding wheels with a vast range of different grinding characteristics. WHAT IS A GRINDING WHEEL? ABRASIVE TYPES CERAMIC ALUMINIUM OXIDE Norton SG, Norton Quantum are patented ceramic forms of aluminium oxide that are harder and sharper than conventional abrasive grains. The ceramic grain has a unique microcrystalline structure and when used in a grinding operation this microstructure becomes self-sharpening. This leads to a reduction in the need for wheel dressing and a considerably cooler cutting action. ALUMINIUM OXIDE Generally recommended for grinding materials of high tensile strength, such as stainless steel and tool steels, but it can also be used on some high tensile aluminium and bronze alloys. It is manufactured in varying qualities. SILICON CARBIDE Harder than aluminium oxide with a very sharp abrasive grain shape. It is recommended for grinding relatively soft materials such as aluminium or cast iron as well as grinding extremely hard materials such as cemented carbide. ZIRCONIA ALUMINA For use in rough grinding applications where high stock removal is required. Associated with high tech resin bonds. ) e (2) xide (2) Brown Aluminum Oxide (2, 7) Heat-treat d Aluminum Oxide (2) Zirconia Alumina (8) Ceramic Alumina (9) Abrasive Types E ery (6) Garnet (5) Silicon Carbide (4) Light Brown Aluminum Oxide (2) Brown Aluminum Oxide (2, 7) Heat-treated Aluminum Oxide (2) Zirconi A a (8) Ceramic Alumina (9) e(2()2, 7) m Oxide (2) BONDED ABRASIVES
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