Preparation of cast iron surface plate before sanding is important. The first problem is choice of plates, then is pressure sand method, specifications of sand, we should be aware of these problems.
The hardness of the plate is between HB (130 ~ 250). We can use low hardness of the plate pressure sand, embedded coarse sand easily, suitable for rough research, repair out of the block surface roughness is relatively low, the surface is white.
The use of high hardness of the plate, embedded grit is difficult, easy to embed fine sand, wear resistance is not ideal, repair the amount of block surface roughness, color is luster.