NNU4976K bearing: complete specifications & equivalents

Specification table

Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01

Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.

Cross references & equivalents

Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.

How the NNU4976K model number is decoded

For pure radial duty on a 380 mm shaft NTN supplies NNU4976K: two integral ribs on the outer ring and a ribless, separable inner ring; the open execution is rated 1,000 r/min on grease and 1,200 r/min on oil. Numbering ties NNU4976K to its envelope: type code NNU, series NNU4900, 380 mm bore; the 520×140 mm outline therefore swaps dimensionally with other ISO 15 bearings of the same code, though rib arrangements differ by prefix. Line contact between rollers and raceways gives NNU4976K high radial capacity but no tolerance for misalignment: beyond roughly 3–4 arc-minutes the roller ends edge-load and fatigue accelerates. Equivalent-load planning treats NNU4976K as a pure radial bearing: keep P below 1810 kN at the required L10, and let a paired angular-contact or thrust part carry any sustained axial component. Heat the inner ring to max 120 °C for the 380 mm interference fit and support the ring face square during fitting; cocking over a keyway brinells the raceway before first rotation.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• At 380 mm bore, oil-lubricated arrangements toward 1,200 r/min need positive flow and drain design; the 80600 g NNU4976K ring stores enough heat that grease-only duty needs a careful relubrication calculation.
• Wide (22/23) and light (10/49) executions at 380 mm bore share bore but not OD/width; check the full NNU4900 series code before substituting, because housing and shoulder geometry will not interchange.
• The NNU rib arrangement is not interchangeable with another prefix on the same 380 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 520×140 mm envelope matches.
• The NNU rib arrangement is not interchangeable with another prefix on the same 380 mm seat: double row, ribbed outer ring, separable inner. Swapping NU for NJ changes axial location behaviour even though the 520×140 mm envelope matches.
• Wide (22/23) and light (10/49) executions at 380 mm bore share bore but not OD/width; check the full NNU4900 series code before substituting, because housing and shoulder geometry will not interchange.
• The 1810/4050 kN ratings, 315 kN Pu and 80600 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NNU4976K (standard execution); other makes sharing the ISO 15 envelope revise internal geometry without changing the order number, so keep the 2203E reference with the specification for critical drives.