LAUSR

Abstract An investigation was made into the effect of grit size and dressing conditions on specific energy, surface-finish characteristics and wheel wear, with a focus on whether smaller, sharp-dressed grits and larger, dull-dressed grits produce different specific energies and surface-finish distributions, even for the same Ra surface-roughness. Grinding tests were performed and measurements were made of grinding forces, wheel wear, Ra, Rt and surface-height distributions. Observations were made of SEM photos of ground surfaces. Results show that, for a given Ra surface roughness, smaller, sharp-dressed Al2O3 grits give significantly lower specific energies and slightly lower Rt values than larger, dull-dressed grits over a large range of grit sizes. This has significant implications in terms of thermal-damage risk and cycle times. Also, using larger, dull-dressed CBN grits requires too-frequent dressing in order to maintain surface roughness. A new concept is developed, the nominal bond shear stress, which can be used to quantify the risk of grit fracture or bond fracture in a single grit. The fundamental relationships between grit size, grit sharpness and contact mechanisms are discussed and practical recommendations are given.