Flexible grinding tools are flexible thermosetting resin bonded abrasives. The resins most used are derived from PUR and EP product groups. Corundum and SIC are used for the abrasive grit. Diamond grains are also used in specific applications.
Since resins can be fashioned in a variety of ways, it is possible to make tools with a Shore hardness of A 30 (roughly equivalent to the hardness of mattress foam) to D 95 (hardness of an electro-casting compound) Because it is bonded in a specific way, the grain is able to oscillate, which means it is able to grind surfaces very gently and smoothly. As a result, the process ensures a low removal rate and a technically perfect surface.