Machinery's Handbook, 31st Edition
Ball and Roller Bearings 2453 For a thrust bearing the supplementary number would consist of two letters to indicate modifications of design, one digit to indicate tolerances, one letter to indicate lubricants and preservatives, and up to three digits to indicate special requirements. For a needle bearing the supplementary number would consist of up to three letters indi cating cage material or integral seal information or whether the outer ring has a crowned outside surface and one letter to indicate lubricants or preservatives. Dimension Series: Annular ball, cylindrical roller, and self-aligning roller bearings are made in a series of different outside diameters for every given bore diameter and in a series of different widths for every given outside diameter. Thus, each of these bearings belongs to a dimension series that is designated by a two-digit number such as or, 23, 93, etc. The first digit (8, 0, 1, 2, 3, 4, 5, 6 and 9) indicates the width series and the second digit (7, 8, 9, 0, 1, 2, 3, and 4) the diameter series to which the bearing belongs. Similar types of identification codes are used for ball and roller thrust bearings and needle roller bearings. Bearing Tolerances Ball and Roller Bearings.— In order to provide standards of precision for proper applica tion of ball or roller bearings in all types of equipment, five classes of tolerances have been established by the Anti-Friction Bearing Manufacturers Association for ball bearings, three for cylindrical roller bearings and one for spherical roller bearings. These toler- ances are given in Table 2, Table 3, Table 4, Table 5, and Table 6. They are designated as ABEC-1, ABEC-3, ABEC-5, ABEC-7 and ABEC-9 for ball bearings, the ABEC-9 being the most precise, RBEC-1, RBEC-3, and RBEC-5 for roller bearings. In general, bearings to specifications closer than ABEC-1 or RBEC-1 are required because of the need for very precise fits on shaft or housing, to reduce eccentricity or runout of shaft or supported part, or to permit operation at very high speeds. All five classes include tolerances for bore, outside diameter, ring width, and radial runouts of inner and outer rings. ABEC-5, ABEC-7 and ABEC-9 provide added tolerances for parallelism of sides, side runout and groove parallelism with sides. Thrust Bearings.— Anti-Friction Bearing Manufacturers Association and American National Standard tolerance limits for metric single direction thrust ball and roller bear- ings are given in Table 8. Tolerance limits for single direction thrust ball bearings, inch dimensioned are given in Table 7, and for cylindrical thrust roller bearings, inch dimen- sioned in Table 9. Only one class of tolerance limits is established for metric thrust bearings. Radial Needle Roller Bearings.— Tolerance limits for needle roller bearings, drawn cup, without inner ring, inch types NIB, NIBM, NIY, NIYM, NIH, and NIHM are given in Table 10 and for metric types NB, NBM, NY, NYM, NH and NHM in Table 11. Standard tolerance limits for needle roller bearings, with cage, machined ring, without inner ring, inch type NIA are given in Table 12 and for needle roller bearings inner rings, inch type NIR in Table 13.
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