Some manufacturing processes cannot produce the required dimensional accuracy or surface finish• An abrasive is a small, hard particle having sharp edges and an irregular shape• Abrasives is removing of small amounts of material from a surface through a cutting process that produces tiny chips• Grinding wheels can sharpen knives and tools (磨利刀具和工具)• Sandpaper (砂紙) or emery cloth(金剛砂布) can smoothen surfaces and remove sharp corners