32306C bearing: complete specifications & equivalents
The 32306C is a ISO 355 radial bearing sized 30 x 72 x 28.75 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 30 mm |
| Outer diameter D | 72 mm |
| Width B | 28.75 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 88 kN |
| Basic static load rating C0 | 94 kN |
| Limiting speed (mechanical) | 5500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 591 g |
| Manufacturer designation | NTN 32306C |
| 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 & 32300-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.835 in |
| Width B | 1.132 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 21 mm |
| Smallest bore in 32300-series | 20 mm |
| Largest outer diameter in 32300-series | 460 mm |
| Width range across 32300-series | 22.25–154 mm |
| Bore position in 32300-series (smallest first) | 3 of 30 |
| Bore above smallest 32300-series size | 10 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 32306C | 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 32306C model number is decoded
NTN supplies this 30 mm bore tapered roller position as 32306C: one cone assembly, one cup, line-contact rollers and a steel cage, rated 88 kN basic dynamic and 94 kN static on the extra-heavy 32300 family. NTN also quotes this bearing with its ISO 355 dimension-series abbreviation, 5FD, which is the maker-neutral cross-reference for the 30×72 mm envelope; 4T is NTN's own tapered-roller brand mark on the parts. Individually mounted, 32306C takes axial force in one direction only; two bearings are arranged face-to-face (X) or back-to-back (O) according to the moment stiffness and misalignment the shaft requires. The 2.9 kN-per-mm-bore capacity figure for 32306C summarises the 88 kN rating over 30 mm bore; use it to sanity-check an interchange candidate before swapping brands. With a rotating shaft a k5/m5 shaft seat and a press-fit cup are typical catalogue practice for 32306C; reverse the logic if the cup rotates, and re-verify against load direction and magnitude.
Typical equipment & failure modes
Common applications
- industrial gearbox and speed-reducer shafts
- bevel and helical pinion drives with high thrust component
- pump and compressor drive shafts carrying combined load
- machine-tool gearbox and headstock shafts
Known failure patterns
- cone-raceway spalling at the large rib when preload is set too high for the lubricant film
- flaking on one cone only when a back-to-back / face-to-face pair is loaded unevenly by a bent shaft
- smearing on the roller large ends and cone rib after a dry start with preload but no oil film
- pressed-steel cage pocket wear from roller skid at light radial load and high speed
- fretting corrosion on a loose cone seat that creeps under rotating load
Selection pitfalls — read before you substitute
- Hub and pinion bearings of this 30 mm bore class are commonly adjusted in pairs; verify end play against the axle drawing and re-torque after bedding-in rather than trusting the initial preload on 32306C.
- The extra-heavy 32300 family at 30 mm bore (72×28.75 mm assembled) carries more capacity than the lighter 320/329 sections but generates more preload heat; confirm oil availability before running near the 7,300 r/min oil ceiling.
- Never fit the 30 mm cone by hammering the 72 mm cup: force for both press fits goes through the ring faces only, or brinell marks release as noise within the first running hours.
- Minimum load matters at high speed: an unloaded 32306C at a large fraction of 5,500 r/min lets rollers skid and smear the cone rib; spring-preload lightly loaded pair arrangements.
- Never fit the 30 mm cone by hammering the 72 mm cup: force for both press fits goes through the ring faces only, or brinell marks release as noise within the first running hours.
- The 88/94 kN ratings here are NTN Ball and Roller Bearings CAT.No.2203E figures for 32306C (ISO 355 5FD); 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 32306C?
32306C is a metric 4T tapered roller bearing to ISO 355: 30 mm bore, 72 mm outside diameter and 28.75 mm assembled width T (1.181 × 2.835 × 1.132 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 88 kN, C0 94 kN (2203E prints no Pu for this size), grease limiting speed 5,500 r/min, oil speed 7,300 r/min, mass about 591 g. It is an open, separable cone/cup bearing with a pressed-steel cage.
What does the 4T prefix mean on 32306C?
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 (32306C); the lower-case 4t- factory spelling of the code is retained among the search aliases.
How does the 32306C designation encode the 30 mm bore and what is 5FD?
last two digits 06 are the ISO bore code, ×5 = 30 mm (codes 00–03 use the 10/12/15/17 exception table). The 72 mm OD and 28.75 mm assembled T follow the ISO 355 dimension-series plan. 5FD 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 32306C list two speeds, 5,500 and 7,300 r/min?
The lower figure, 5,500 r/min, is the grease-lubricated limiting speed — the mechanical ceiling for the cage, rollers and cone-rib contact. With oil lubrication NTN rates 32306C at 7,300 r/min because oil removes rib-contact heat better. Real limits still depend on preload, oil flow and cooling.
What does the suffix on 32306C mean?
Suffix reading on 32306C: the trailing A/C/D (or E1) letter marks an NTN contact-angle or internal-design revision of the base number, not a seal or clearance code; 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.