The material removal characteristics of a number of types (including monocrystalline and polycrystalline varieties) and sizes of diamond abrasives dispersed in a triethanolamine and stearic acid carrier paste have been investigated quantitatively. The basic investigation was carried out using specimens of annealed brass, but a widely representative range of other materials was also investigated. For all abrasives and almost all specimen materials, the maximum material removal rate was obtained with 2-4 micron m grade of abrasive, the removal rate decreasing rapidly with either increase or decrease in abrasive size from the removal rate decreasing rapidly with either increase or decrease in abrasive size from the optimum value.