The so-called wheel hardness is above abrasive grinding wheel grinding job shedding in the degree of difficulty, we are generally referred to as the wheel hard and soft, suitable for different grinding wheel hardness different workpieces, if wheel too hard, blunt the the abrasive is not timely shedding, will generate a lot of heat, burn the workpiece; if the wheel is too soft, then make the abrasive off too fast and not fully effective.
1, the greater the contact surface grinding wheel and the workpiece, choose softer wheel, on the contrary, on the choice of high hardness grinding wheel;
2, the harder workpiece, the softer selected wheel, the softer parts, the harder the selected wheel;
3, grinding and profile grinding wheel should choose harder to maintain the necessary wheel shape accuracy;
4, the cooling liquid than dry grinding the  grinding wheel  hardness grade 1 to 2 hours;
5, the larger the particle size of the wheel, in order to avoid debris blocked by grinding wheel, generally softer wheel to choose;
6, in the same grinding conditions, with resin bonded grinding wheel vitrified wheel than the hardness of 1-2 small higher grade;
7, end mill compared with the circumference of the grinding should choose something softer wheel;
8, wheel rotation speed is high, the hardness of the optional soft wheel 1 to 2 small magnitude.
9, the grinding of the workpiece poor thermal conductivity should be selected softer wheel;
10, grinding soft and toughness of non-ferrous metals, the hardness to be elected was softer.