33018U bearing: complete specifications & equivalents
The 33018U is a ISO 355 radial bearing sized 90 x 140 x 39 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 90 mm |
| Outer diameter D | 140 mm |
| Width B | 39 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 238 kN |
| Basic static load rating C0 | 360 kN |
| Fatigue load limit Pu | 42 kN |
| Limiting speed (mechanical) | 2500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2220 g |
| Manufacturer designation | NTN 33018U |
| 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 | 3.543 in |
|---|---|
| Outer diameter D | 5.512 in |
| Width B | 1.535 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 25 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) | 16 of 24 |
| Bore above smallest 33000-series size | 65 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 33018U | 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 33018U model number is decoded
For a 90 mm shaft with a thrust component, NTN lists 33018U, a metric 4T tapered roller bearing of 238 kN C and 360 kN C0 inside the 140 mm OD, 39 mm-wide assembled set. The last two digits 18 are the ISO bore code, ×5 = 90 mm (codes 00–03 use the 10/12/15/17 exception table) under the ISO 355 numbering; the 39 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 33018U, not only the raceway. Catalogue mass of the 33018U set is 2220 g (0.087 lb cone + cup); abutment and shaft shoulder design must carry that mass square to the axis. With a rotating shaft a k5/m5 shaft seat and a press-fit cup are typical catalogue practice for 33018U; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- large agricultural and forestry machine axles
- heavy industrial gearboxes and crane travel drives
- rolling-mill auxiliary and pinion-stand shafts
- large conveyor and bucket-elevator pulleys
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
- edge loading when shaft deflection exceeds the few arc-minutes of misalignment the adjusted pair allows
Selection pitfalls — read before you substitute
- Mount the 90 mm cone by induction heating (max 120 °C) and the cup with a press sleeve; the 2220 g ring mass makes cocking during fitting a direct raceway-brinelling risk.
- The thin 39 mm section of 33018U is built for low friction and tight envelopes, not the heavy preload of a 322/323 set; over-tightening adjustment on this 90 mm bore smears the roller ends against the rib.
- The U/UTG/X/C/CA/D suffix variants of a base number share the bore but not the article: ordering 33018U by size alone can deliver the wrong contact-angle execution for a pinion position.
- Minimum load matters at high speed: an unloaded 33018U at a large fraction of 2,500 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- Back-to-back and face-to-face arrangements react differently to shaft bending: pick the pair orientation for the moment load before locking the 90 mm shoulder geometry, because retrofitting flips the cups.
- The 238/360 kN ratings and 42 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 33018U (ISO 355 2CE); 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 33018U?
33018U is a metric 4T tapered roller bearing to ISO 355: 90 mm bore, 140 mm outside diameter and 39 mm assembled width T (3.543 × 5.512 × 1.535 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 238 kN, C0 360 kN, Pu 42 kN, grease limiting speed 2,500 r/min, oil speed 3,300 r/min, mass about 2220 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 33018U?
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 (33018U); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 33018U designation encode the 90 mm bore and what is 2CE?
last two digits 18 are the ISO bore code, ×5 = 90 mm (codes 00–03 use the 10/12/15/17 exception table). The 140 mm OD and 39 mm assembled T follow the ISO 355 dimension-series plan. 2CE 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 33018U list two speeds, 2,500 and 3,300 r/min?
The lower figure, 2,500 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 33018U at 3,300 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 33018U mean?
Suffix reading on 33018U: 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.