Fe, Cr, Ti, Ni, etc, can’t be machined by diamond, because these metal elements will cause a series of chemical reactions, such as oxidation or graphitization reaction with diamond, the diamond grains will wear off quickly during the grinding process of the above-mentioned materials. CBN(Cubic Boron Nitride), as the second hardest material after diamond and with similar properties to diamond, is used for machining non-diamond-machinable metals. CBN is the best suitable abrasive for grinding ferrous materials. You will hardly generate a high temperature because CBN has an extremely good conductivity for temperature, so the heat generated is dispersed quickly.