This standard specifies the overall dimensions, technical requirements, testing methods, inspection rules and packaging of 2344, 2347, 2349 and 2349X series bidirectional thrust angular contact ball bearings (hereinafter referred to as bearings) for machine tool spindles. This standard applies to 2344, 2347, 2349 and 2349X series bidirectional thrust angular contact ball bearings for machine tool spindles, and is provided for manufacturer production, inspection and user acceptance.