31320XU bearing: complete specifications & equivalents
The 31320XU is a ISO 355 radial bearing sized 100 x 215 x 56.5 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 100 mm |
| Outer diameter D | 215 mm |
| Width B | 56.5 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 395 kN |
| Basic static load rating C0 | 435 kN |
| Fatigue load limit Pu | 46 kN |
| Limiting speed (mechanical) | 1800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 8700 g |
| Manufacturer designation | NTN 31320XU |
| 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 & 31300-series range
| Bore d | 3.937 in |
|---|---|
| Outer diameter D | 8.465 in |
| Width B | 2.224 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 57.5 mm |
| Smallest bore in 31300-series | 25 mm |
| Largest outer diameter in 31300-series | 320 mm |
| Width range across 31300-series | 18.25–82 mm |
| Bore position in 31300-series (smallest first) | 16 of 22 |
| Bore above smallest 31300-series size | 75 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 31320XU | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; brand-specific OEM equivalents (NSK/FAG/NTN) pending multi-source data. |
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 31320XU model number is decoded
31320XU belongs to the NTN metric 4T tapered roller range (steep-angle 31300 family for high axial load share); the open bearing leaves sealing to the application and is normally ordered and mounted as an adjustable matched pair. Digit by digit, the bare number identifies the steep-angle 31300 family for high axial load share and a bore code resolving to 100 mm; 215 mm OD and 56.5 mm assembled T are the matching ISO 355 boundary dimensions shared with other makers of the same dimension series. NTN adjusts these bearings by cup or cone position rather than shipping a preloaded set; the mounting drawing must state end play or preload for 31320XU, since running clearance is set during assembly. The 57.5 mm section height over the 100 mm bore positions the load centre; axial location of the pair depends on that contact line, so spacer faces must be square within the P0 tolerance of the bearing. With a rotating shaft a k5/m5 shaft seat and a press-fit cup are typical catalogue practice for 31320XU; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- heavy industrial gearboxes and crane travel drives
- rolling-mill auxiliary and pinion-stand shafts
- large conveyor and bucket-elevator pulleys
- mineral-processing feeder and crusher auxiliaries
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
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- indentation of the raceways by hard particles in unsealed open arrangements
Selection pitfalls — read before you substitute
- Mount the 100 mm cone by induction heating (max 120 °C) and the cup with a press sleeve; the 8700 g ring mass makes cocking during fitting a direct raceway-brinelling risk.
- The steeper contact angle of the steep-angle 31300 family for high axial load share raises axial capacity but lowers the speed ceiling against a 302/322 bearing at 100 mm bore; do not swap to the lighter family without re-checking the 1,800 r/min grease limit and the thrust load split.
- The U/UTG/X/C/CA/D suffix variants of a base number share the bore but not the article: ordering 31320XU by size alone can deliver the wrong contact-angle execution for a pinion position.
- The 57.5 mm section leaves little room for an oversized shaft fillet; check the mounting-chamfer table for 31320XU or the ring will bottom out on the radius instead of the shoulder face.
- On slash-size and T-code bearings confirm the full code on both cone and cup before fitting: the 100 mm bore alone does not identify the cup, and a mismatched cone/cup set has no catalogue rating.
- The 395/435 kN ratings and 46 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 31320XU (ISO 355 7GB); 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 31320XU?
31320XU is a metric 4T tapered roller bearing to ISO 355: 100 mm bore, 215 mm outside diameter and 56.5 mm assembled width T (3.937 × 8.465 × 2.224 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 395 kN, C0 435 kN, Pu 46 kN, grease limiting speed 1,800 r/min, oil speed 2,400 r/min, mass about 8700 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 31320XU?
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 (31320XU); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 31320XU designation encode the 100 mm bore and what is 7GB?
last two digits 20 are the ISO bore code, ×5 = 100 mm (codes 00–03 use the 10/12/15/17 exception table). The 215 mm OD and 56.5 mm assembled T follow the ISO 355 dimension-series plan. 7GB 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 31320XU list two speeds, 1,800 and 2,400 r/min?
The lower figure, 1,800 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 31320XU at 2,400 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 31320XU mean?
Suffix reading on 31320XU: XU combines the X ISO boundary section with the U uprated internal design; 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.