NN4921 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 NN4921 model number is decoded

For pure radial duty on a 105 mm shaft NTN supplies NN4921: two integral ribs on the outer ring and a ribless, separable inner ring; the open execution is rated 4,100 r/min on grease and 4,800 r/min on oil. The leading NN defines the rib arrangement (double row, ribbed inner ring, separable outer); the dimension-series digits and the two-digit bore code resolve to 105 mm, with 145 mm OD and 40 mm width from the ISO 15 general plan. Minimum radial load matters: an unloaded NN4921 at high speed skids its rollers and smears the raceway; spring preload or the rotor weight typically covers the requirement in motors and pumps. The 1.4 kN-per-mm-bore figure (147 kN over 105 mm) lets a NN4921 interchange candidate be screened quickly against the same-envelope ball or roller alternatives. Keep the open bearing wrapped until fitting: the line-contact raceways of the 105 mm bore indent under a single hard particle, and the steel cage provides no sealing of its own.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Induction-heat the 105 mm inner ring (max 120 °C) and mount it before fitting the outer ring; the ring mass makes square guidance essential — driving through the rollers brinells the 145 mm raceway.
• Do not replace NN4921 with a deep-groove ball bearing on rating alone: line contact gives 147 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
• Open NN4921 units need application-supplied sealing and a defined lubricant schedule; film thickness is the first failure mode for line contact when viscosity drops at the 105 mm contact.
• The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 147/268 kN pair here belongs to NN4921 as printed, not to the bare size.
• Do not replace NN4921 with a deep-groove ball bearing on rating alone: line contact gives 147 kN radial capacity but the bearing cannot carry the thrust duty a ball bearing can and misalignment tolerance is only 3–4 arc-minutes.
• The 147/268 kN ratings, 30.5 kN Pu and 1820 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NN4921 (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.