Grinders are tools used for grinding and polishing various materials such as wood, metal, plastic and glass. There are several types of grinders, including angle grinders, belt grinders, disc grinders, and bench grinders. Angle grinders are hand-held grinders that use a rotating wheel to grind or cut materials. They are commonly used in metalworking applications. Belt sanders use a long, moving abrasive belt to sand or polish materials. They can be used to work on wood, metal and plastic. Disc grinders have a rotating grinding wheel that is used to grind materials such as metal and wood. They can also be used to sharpen tools such as scissors, chisels and knives. Bench grinders are stationary grinders that are mounted on a table or workbench. They can be used to grind and polish small parts. It is important to pay attention to safety when grinding and wear protective clothing such as gloves and eye protection. In addition, grinders should always be properly maintained to ensure they work safely and effectively.