Proxxon High Quality Carborundum grinding bits High quality bits and sets of quality base materials of consistent hardness. Various shapes for widest possible range of applications. For working especially hard materials such as cast irn, steel as well as hard metal alloys. Accurately dimensioned shafts of 2.35 or 3.0mm ensure maximum concentricity. Carborundum grinding bits - No 28772 size 5.0mm pack of 5 Carborundum grinding bits - No 28778 size 7.0mm pack of 5 Carborundum grinding bits - No 28776 size 6.0mm pack of 5 Carborundum grinding bits - No 28772 size 5.0mm pack of 5