In rough grinding, the grinding allowance is large and the surface roughness requirement is high, so coarser abrasive grains should be used. Because the abrasive grit are coarse and have large pores, the grinding depth is large and the grinding wheel is not easy to clog and heat up. In fine grinding, the allowance is small and the roughness value required is small, so finer abrasive grains can be selected. Generally speaking, the finer the abrasive grains, the better the grinding surface roughness.
What does the commonly used term "how many mesh" mean?
The mesh number refers to the number of holes per square inch on the screen. 50 mesh means 50 holes per square inch, and 500 mesh means 500 holes per square inch. The higher the mesh number, the more holes there are, and the smaller the particle size of the abrasive that is screened, the finer the particle size. The filter separates the abrasive particles into different sizes.
The selection of abrasive grit size is related to the properties of the workpiece and the grinding process parameters, especially the roughness of the workpiece surface after grinding, the feed rate, and the maximum single-knife cutting depth.
As shown in the figure, the strip particles are within the width limit, but the length limit is exceeded. Such particles will also leak through the screen and mix into the 120/140 abrasive. When made into a grinding wheel, it is easy to scratch the workpiece. If the fine-grained grinding wheel used for fine grinding scratches the workpiece, the workpiece will be scrapped. Therefore, W10 and coarse-grained particles can generally be screened several times to reduce strips and flakes, while W10 and fine-grained micro-powders can generally be reduced by increasing the number of sedimentation times to reduce strips and large particles. In addition, the quality of the screen must be qualified.
"Grit size" is directly related to the quality of grinding, especially the surface roughness. For abrasives of the same particle size, the sharper the abrasive grains, the higher the processing efficiency, and the rounder the grains, the better the surface quality (the smaller the surface roughness value). In general, rounded grains are stronger than sharp grains. The strength of the abrasive is related to the density of the crystal structure of the abrasive itself, that is, when the abrasive grit edge is still quite sharp, it can withstand external pressure without being broken. Abrasives with poor strength have abrasive grains that crush quickly, have low cutting ability, and have a short service life.
In order to obtain better grinding, the abrasive grit should have sufficient strength. A superhard grinding wheel requires both rounded abrasive grains to ensure the surface quality of the processing and relatively sharp abrasive grains to improve its processing efficiency.
