The right grinding material requires that you consider the material hardness, the piece of metal to be worked on and the type of finish required.
The first mistake: Grinding wheel
Most of the grinding wheels are made up of the abrasive and the bond used for cutting and holding the abrasive in place respectively. The grit determines the size of the abrasive to be used. When the grit number is low, a smaller abrasive must be used.Using a too coarse of grinding wheel for the surface finish may not give you the required results. Instead, you can obtain a finer finish by slowing down the dressing federate even though it can result in dulling the abrasive. A dull wheel generates more heat and result in a lot of grinding force that is not good for quality productivity. Using a grit that has sharp abrasive grains will give better results compared to a grit wheel with abrasive grains. The following chart gives the size of grit required for the given finish.
Mistake 2: Dressing
Regular dressing may not be necessary. In fact a proper grinding wheel can allow for grinding multiple wheels without necessarily dressing the wheel. If more material is removed from the abrasive grain, it becomes dull. Thus, dressing every part may not be necessary. Reducing the frequency of dress has an added advantage; it reduces the cycle time extending the life of the dressing diamond and the grinding wheel. This reduces the cost and enhances productivity.
Note: the diamond dresser can also have an effect on the quality as well as the general productivity. Thus, the simplest method of dressing is where a single point diamond is used. However, care must be taken when using this single point diamond since it requires frequent rotation. When this is done regularly, the single diamond will wear out and develop a flat.
A single point diamond that has developed a flat makes the abrasive grain to become dull even when the grinding wheel is dressed. To dress the grinding wheel rotary dressing which uses an electric spindle to rotate may be employed. The rotary dressing is thus, a better alternative since it provides a consistent dress and reduces the possibility of the dressing disc to wear and develop flats as it is in the case of a single point diamond.
This was valuable information acquired years ago and improved productivity and the quality of my CNC machining endeavours.