Effect of grinding conditions on the surface finish and compaction of cermet surfaces

Abstract

1. It has been found that in grinding porous cermets the quality of the ground surface is formed in a different way from the case of solid metals. 2. In grinding porous cermets it is not possible to obtain a machined but not compacted surface. By varying the grinding conditions it is only possible to increase or reduce slightly the degree of compaction of the surface layers from a certain standard depending on the properties of the material being machined. 3. In the case of cermets of the same chemical composition the compaction process of the surface layer is strongly affected by the porosity; its increase, with other conditions remaining unchanged, results in a considerable inincrease of compaction. 4. It was found that in grinding hardened chromium steel the porosity of 10–30% the compaction increases 4 times and that the increase is even greater in the case of porous iron. 5. If a high degree of compaction of a ground surface is needed lower cross feed rates should be used (0.3–0.6 mm/pass) with a table feed of 13–18 m/min and a depth of cut of 0.05–0.1 mm; medium-hardness corundum wheels should be used. 6. When the compaction of the surface layer is undesirable, higher cross feed rates should be used (1.7–3.0 mm/pass) with a table feed of 6–12 m/min and a depth of cut of 0.01–0.03 mm; frequently hard corundum wheels should be used. 7. In grinding chromium-steel and iron cermets the 9–10th class of surface finish can be obtained with cross-feed rates of 0.3–2.0 mm/pass, table-feed rates of 6–15 m/min, depths of cut of 0.01–0.03 mm using, for example, EB20SM2K, EB40SM2K wheels.