What are the expected surface finishes when machining magnetic materials?
Magnets may be shaped using any number of machining processes, such as cutting, grinding, EDM, or even abrasive water-jet. Typically, most magnets are brought to finished size by utilizing a grinding process. Most grinders will produce at least a 16G surface finish on most magnets using a standard grinding wheel.(When grinding Alnico, surface finish would be improved [8G], due to material hardness). Blanchard grinders will produce at least a 32BL surface finish on all magnets using a standard wheel. (Again, Alnico would theoretically be higher [16BL] due to the hardness.) Other machining processes (EDM, water-jet) can be controlled by altering cutting speeds in order to produce similar surface finishes to what is seen in grinding processes. Therefore, the easiest way to remember surface finish grades on magnets is to remember the numbers 16 and 32.
