NEEDLE ROLLER BEARINGS INNER RINGS When it becomes impractical to meet the shaft raceway design requirements (hardness, case depth, surface fi nish, etc.) outlined in the engineering section of this catalog, standard inner rings may be used with metric series drawn cup bearings. It is suggested that when metric series inner rings are used with metric series drawn cup bearings, they should be mounted with a loose transition fi t on the shaft using g5 shaft diameter tolerance. The inner ring should be end-clamped against a shoulder. If a tight transition fi t must be used (shaft diameter tolerance h5) to keep the inner ring from rotating relative to the shaft, the inner ring outer diameter, as mounted, must not exceed the raceway diameter required by the drawn cup bearing for the particular application. In case the outer diameter of the inner ring, when mounted on the shaft, exceeds the required raceway diameter for the matching drawn cup bearing, it should be ground to proper diameter while mounted on the shaft. When such exacting close control of radial internal clearance is not required the user may select g6 or h5 shaft diameter tolerances. LOAD RATING FACTORS DYNAMIC LOADS Drawn cup needle roller bearings can accommodate only radial loads. P = Fr P = The maximum dynamic radial load that may be applied to a drawn cup bearing based on the dynamic load rating, Cr given in the bearing tables. This load should be < Cr/3. STATIC LOADS f0 = C0 P0 f0 = static load safety factor C0 = basic static load rating (kN) P0 = maximum applied static load (kN) To ensure satisfactory operation of drawn cup needle roller bearings, under all types of conditions, the static load safety factor f0 should be > 3. INSPECTION OF DRAWN CUP NEEDLE ROLLER BEARINGS Although the bearing cup is accurately drawn from strip steel, because of its fairly thin section, it may go out-of-round during heat treatment. When the bearing is pressed into a true round housing, or ring gage of correct size and wall thickness, it becomes round and is sized properly. For this reason, it is incorrect to inspect an unmounted drawn cup bearing by measuring the outer diameter. The correct method for inspecting the bearing size is to: 1. Press the bearing into a ring gage of proper size. 2. Plug the bearing bore with the appropriate “go” and “no go” gages, or measure it with a tapered arbor (lathe mandrel). • HK and BK series The "go" gage size is the minimum needle roller complement bore diameter. The "no go" gage size is larger than the maximum needle roller complement bore diameter by 0.002 mm (0.0001 in). (Table B2-2) • BTM, BHTM, BSM, BKM, BM and YM series The inspection gage (ring gage and plug gage) sizes are listed in Table B2-3. NOTE SPECIAL BEARINGS. There are bearings available with other cage designs, and materials such as reinforced engineered polymer for use where operating conditions permit. Table B2-1. Metric mounting fi ts Bearing type Operating condition Shaft fi t (recommended internal radial clearances) Housing fi t (recommended internal radial clearances) HK, BK, HKRS, HK.2RS, BTM, BHTM, BSM, BKM (caged) One piece heavy section steel or cast iron housing h5 (h6) N6 (N7) Housing material of low rigidity h5 (h6) R6 (R7) Outer ring rotation (one piece heavy section steel or cast iron housing) f5 (f6) R6 (R7) Oscillating motion j5 (j6) (1) BM, BHM, YM (full complement) One piece heavy section steel or cast iron housing h5 (h6) H6 (H7) Housing material of low rigidity h5 (h6) M6 (M7) Outer ring rotation (one piece heavy section steel or cast iron housing) f5 (f6) M6 (M7) Oscillating motion j5 (j6) (1) (1) Tolerance dependent on housing design. B B-2-8 NEEDLE ROLLER BEARINGS