This International Standard specifies the maximum permissible values of unbalances for bonded abrasive wheels with an outside diameter D ≥ 125 mm and maximum operating speed vs ≥ 16 m/s, in the as-delivered condition. It also specifies the method for measuring the unbalance and the practical method for testing whether a grinding wheel is acceptable or not. This International Standard is applicable to bonded abrasive wheels in the as-delivered condition. This International Standard is not applicable to — diamond, cubic boron nitride or natural stone grinding wheels, or — centreless control wheels, lapping and disc wheels, ball wheels or glass grinding wheels. NOTE 1 The values given refer to the grinding wheel itself, independent of any unbalance which may exist in the balancing arbor or in the means of fastening it to this arbor. These various elements, together with the flanges or hub-flanges, are assumed to be balanced, homogeneous and free from geometrical defects. NOTE 2 The effects of unbalance are basically — additional stresses on the arbor, the machine and its mounting, — excessive wear of the bearings, — vibration prejudicial to the quality of machining and increased internal stresses in the grinding wheel, and increased operator fatigue.