A roller bearing is a type of bearing used in band saws, mill drill machines, or other machinery to reduce friction and support rotating components, such as shafts or spindles. Roller bearings consist of cylindrical rolling elements that move between an inner and outer race, distributing the load over a larger contact area and providing low-friction, smooth motion. In band saws, roller bearings are commonly used as blade guides, helping to maintain proper blade alignment and minimize blade deflection.