The Norton 20X high-performance type 29 depressed- center zirconia alumina abrasive flap disc has a phenolic resin backing for reinforcement and a threaded hole for attachment to a right-angle grinder. The zirconia alumina abrasive is self-sharpening and more durable than aluminum oxide, which makes it suitable for fast material removal rates and aggressive grinding. The phenolic resin backing plate keeps the disc from scratching the workpiece. The type 29 angled style disc offers durability and reinforcement for use in metal fabrication, weld blending, deburring, stock removal, cleaning, stripping, and finishing in one step. The female-threaded central hole twists onto a threaded arbor. The disc shape is angled for maximum workpiece contact and is commonly used with right-angle grinders at a 15- to 25-degree angle to dissipate heat. Recommended Grit Sizes 80 grit (fine) For surface preparation before applying a stain, primer, or sealer 40 or 60 grit (medium) For blending and moderate material removal Abrasive flap discs are made from overlapping pieces of coated abrasive attached to a hub. They help reduce finishing time and cost by grinding and finishing in the same step, such as when removing a weld bead and smoothing the workpiece around the weld. Flap discs are coated, meaning an adhesive is used to attach the abrasive grains to a backing of paper, plastic, or cloth. The action of a flap disc is much like that of a sanding disc: the grinding or polishing occurs on the face of the disc. They are used for a variety of applications from shaping a part to fine finishing, depending on the grit size. Low grit numbers like 40 are coarse (with fewer, larger grains) and remove excess material and shape parts. High grit numbers like 400 are fine (with more, smaller grains) and help create a smooth surface finish. Norton Abrasives manufactures sanding, grinding, and polishing abrasives. The company, founded in 1885, meets International Organization for Standardization (ISO) standards 9000 and 14001 for quality and environmental management.