Description The Klingspor PS 21 FK zirconia paper discs has a formulated recipe for this abrasive disc such that it will produce optimal results during rough and finish sanding on stainless steel. This abrasive is also an excellent choice for work on steel and metals. Its most distinguishing features are its aggressive abrasive performance and its long service life. Klingspor makes the abrasive disc PS 21 FK available in a great number of different grit sizes. It also comes in a wide selection of diameters. The PS 21 FK ? hard, extra tough and self-sharpening zirconia on a paper backing The Klingspor abrasive disc PS 21 FK is fastened by a hook and loop connection, making it a cinch to fit it on a sander with hook and loop backing pads. It is furnished with a backing made of heavy F-weight paper. The abrasive grain is applied to this backing. Consisting of zirconia, this abrasive is made synthetically – just as all other grains used by Klingspor. The synthetic manufacturing process preserves the product’s high quality and exceptional characteristics. Zirconia is hard, exceedingly tough and possesses a uniform, crystalline structure. Better yet, this aggressive grain is also self-sharpening. This feature allows the abrasive disc to deliver outstanding service life. Closely coated abrasive grain ? ideal for processing steel and metal Klingspor equips the abrasive disc PS 21 FK with zirconia and applies it to the paper backing with a close coating. This coating ensures that the paper is covered almost completely with abrasive grain. The large number of grain points placed closely to each other allow for a high stock removal rate. What is more, the close coating extends the service life of the abrasive significantly. It is used primarily for abrasive sheets, discs, belts and other abrasives designed for work on steel and metal. Klingspor always uses a synthetic resin to bond the abrasive grain in place on the backing. An even stronger bond is achieved by the top bonding, which is also referred to as the size coat. Klingspor uses synthetic resin for all of their abrasives as it is marked by exceptional strength and adhesive force. The top binding also supports the abrasive grains against forces that act on them from the side during the sanding process. The quality and thickness of the base coat and top size coat, whose recipe Klingspor always formulates to match each product perfectly, also plays a major role in achieving excellent service life.