Machine tool users, such as manufacturers of hard disk drive components for personal computers and other IT products, demand higher precision during the manufacturing process. Other machine tool users, such as manufacturers of aerospace components, demand higher speeds and reduced cycle times. Machine tool manufacturers respond by continuing to improve and develop their machines to offer users higher speeds, improved surface finishes and thus increased productivity and lean manufacturing. This paper examines the design of cylindrical roller bearings especially for main spindles of machine tools that require high-speed or high-accuracy performance.