33021U bearing: complete specifications & equivalents
The 33021U is a ISO 355 radial bearing sized 105 x 160 x 43 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 105 mm |
| Outer diameter D | 160 mm |
| Width B | 43 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 272 kN |
| Basic static load rating C0 | 420 kN |
| Fatigue load limit Pu | 47 kN |
| Limiting speed (mechanical) | 2100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3000 g |
| Manufacturer designation | NTN 33021U |
| Standard | ISO 355 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
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.
Dimensions in inches & 33000-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 6.299 in |
| Width B | 1.693 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 27.5 mm |
| Smallest bore in 33000-series | 25 mm |
| Largest outer diameter in 33000-series | 225 mm |
| Width range across 33000-series | 17–59 mm |
| Bore position in 33000-series (smallest first) | 19 of 24 |
| Bore above smallest 33000-series size | 80 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 33021U | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
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 33021U model number is decoded
33021U is a metric single-row tapered roller bearing in the NTN 4T programme: a pressed-steel cage guides profiled rollers between a separable cone and cup on the 105×160 mm ISO 355 envelope, with 43 mm overall assembled width T. The last two digits 21 are the ISO bore code, ×5 = 105 mm (codes 00–03 use the 10/12/15/17 exception table) under the ISO 355 numbering; the 43 mm value printed here is T, the width of the fully assembled cone-plus-cup set, not the inner-ring width alone. The rollers run with their large ends against the cone's integral guide rib; the rib/end-flange contact carries the thrust component and is the reason lubricant must reach the rib face of 33021U, not only the raceway. Selection: C 272 kN against C0 420 kN gives a C0/C ratio of 1.54 for the 105 mm bore, and the equivalent combined load must keep below the rating at the target L10 with the pair counted as one unit. With a rotating shaft a m6/n6 shaft seat and a press-fit cup are typical catalogue practice for 33021U; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- paper-machine press-section rolls
- large agricultural and forestry machine axles
- heavy industrial gearboxes and crane travel drives
- rolling-mill auxiliary and pinion-stand shafts
Known failure patterns
- cup creep and housing fretting when the specified outer-ring press fit is not achieved
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- cage damage from a mounting blow delivered through the roller complement instead of the ring face
- false brinelling on a stationary paired set exposed to external vibration
Selection pitfalls — read before you substitute
- Mount the 105 mm cone by induction heating (max 120 °C) and the cup with a press sleeve; the 3000 g ring mass makes cocking during fitting a direct raceway-brinelling risk.
- The thin 43 mm section of 33021U is built for low friction and tight envelopes, not the heavy preload of a 322/323 set; over-tightening adjustment on this 105 mm bore smears the roller ends against the rib.
- Minimum load matters at high speed: an unloaded 33021U at a large fraction of 2,100 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- Do not confuse T (43 mm assembled width of cone + cup) with the cone width when drawing spacers; an abutment sized to T instead of the ring width leaves the cup unseated.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 105 mm shoulder geometry, because retrofitting flips the cups.
- The 272/420 kN ratings and 47 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 33021U (ISO 355 2DE); internal geometry legitimately differs between manufacturers, so re-verify ratings, adjustment and suffix before substituting another make on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 33021U?
33021U is a metric 4T tapered roller bearing to ISO 355: 105 mm bore, 160 mm outside diameter and 43 mm assembled width T (4.134 × 6.299 × 1.693 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 272 kN, C0 420 kN, Pu 47 kN, grease limiting speed 2,100 r/min, oil speed 2,800 r/min, mass about 3000 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 33021U?
4T is NTN's tapered roller bearing brand mark, stamped on the cone and cup in the factory. It identifies the NTN 4T programme and is not a dimension, so the catalogue and this page list the bare ISO 355 number (33021U); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 33021U designation encode the 105 mm bore and what is 2DE?
last two digits 21 are the ISO bore code, ×5 = 105 mm (codes 00–03 use the 10/12/15/17 exception table). The 160 mm OD and 43 mm assembled T follow the ISO 355 dimension-series plan. 2DE is the maker-neutral ISO 355 abbreviation for this dimension series (the same code other manufacturers print); 4T is NTN's own brand mark.
Why does 33021U list two speeds, 2,100 and 2,800 r/min?
The lower figure, 2,100 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 33021U at 2,800 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 33021U mean?
Suffix reading on 33021U: U marks the reinforced/uprated internal design of the bare number, a separate order number with higher load capacity than the basic execution; the suffix is part of the order number and the variants are not interchangeable articles.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.