NU311-NTN 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 NU311-NTN model number is decoded

NU311 is an NTN NU cylindrical roller bearing: two integral ribs on the outer ring and a ribless, separable inner ring — a non-locating bearing that lets the shaft float axially, inside the 55×120×29 mm ISO 15 envelope. The leading NU defines the rib arrangement (outer ring ribbed, inner ring ribless); the dimension-series digits and the two-digit bore code resolve to 55 mm, with 120 mm OD and 29 mm width from the ISO 15 general plan. Minimum radial load matters: an unloaded NU311 at high speed skids its rollers and smears the raceway; spring preload or the rotor weight typically covers the requirement in motors and pumps. Equivalent-load planning treats NU311 as a pure radial bearing: keep P below 123 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 55 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

• On this 55 mm bore, shaft thermal growth can preload the inner ring if the fit is too tight; verify residual interference at temperature and confirm the float ring still slides after mounting NU311.
• Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 120 mm race brinells and releases as vibration within hours.
• If the shaft must be located both ways, do not use NU311 alone: pair it with a locating bearing or specify the NUP execution with the matching loose rib ring from the 2203E table.
• Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 120 mm race brinells and releases as vibration within hours.
• Do not replace NU311 with a deep-groove ball bearing on rating alone: line contact gives 123 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 123/111 kN ratings, 13.6 kN Pu and 1420 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU311 (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.