NJ321 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 NJ321 model number is decoded

For pure radial duty on a 105 mm shaft NTN supplies NJ321: two integral ribs on the inner ring and one rib on the outer ring; the open execution is rated 3,100 r/min on grease and 3,700 r/min on oil. Digit by digit, NJ321 reads as NJ (inner ring two ribs + one outer rib), ISO 15 series, and bore 105 mm; trailing letters such as EA or E mark the cage/capacity execution and are part of the order number. NTN ships these bearings open with normal (CN) radial clearance and P0 tolerance as standard; precision classes and C3/C4 clearance are separate order suffixes, not part of NJ321. The 105 mm (4.134 in) bore and 225 mm (8.858 in) OD are ISO 15 boundary values; fillet and shoulder dimensions must still come from the NTN mounting table for the 49 mm-wide ring. Heat the inner ring to max 120 °C for the 105 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

• 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 225 mm raceway.
• Wide (22/23) and light (10/49) executions at 105 mm bore share bore but not OD/width; check the full NJ300 series code before substituting, because housing and shoulder geometry will not interchange.
• The NJ rib arrangement is not interchangeable with another prefix on the same 105 mm seat: inner ring two ribs + one outer rib. Swapping NU for NJ changes axial location behaviour even though the 225×49 mm envelope matches.
• Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 225 mm race brinells and releases as vibration within hours.
• Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 225 mm race brinells and releases as vibration within hours.
• The 355/360 kN ratings, 37.5 kN Pu and 8330 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NJ321 (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.