29318 bearing: complete specifications & equivalents
The 29318 is a ISO 104 radial bearing sized 90 x 155 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 | 155 mm |
| Width B | 39 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 320 kN |
| Basic static load rating C0 | 915 kN |
| Fatigue load limit Pu | 84 kN |
| Limiting speed (mechanical) | 2300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3080 g |
| Manufacturer designation | NTN 29318 |
| Standard | ISO 104 |
| 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 & 29300-series range
| Bore d | 3.543 in |
|---|---|
| Outer diameter D | 6.102 in |
| Width B | 1.535 in |
| ISO bore code | 18 |
| Radial section height (D−d)/2 | 32.5 mm |
| Smallest bore in 29300-series | 85 mm |
| Largest outer diameter in 29300-series | 1180 mm |
| Width range across 29300-series | 39–230 mm |
| Bore position in 29300-series (smallest first) | 2 of 31 |
| Bore above smallest 29300-series size | 5 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 29318-E | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 90×155×39 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 29318 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 29318 appears as a medium-section 29300 spherical-thrust family bearing with a 90 mm shaft washer, 155 mm across the housing washer and 39 mm of height. NTN builds the number from 293 is the dimension series (medium-section 29300 spherical-thrust family); 18 encodes the 90 mm bore (bore code x 5). The spherical housing raceway lets the shaft washer align itself as the seats settle — the property that keeps the 915 kN static rating honest in real housings. Against a thrust ball bearing of the same 90 mm bore, this bearing carries many times the load at lower speed — the trade is oil lubrication and price. After filling with oil, rotate slowly and watch torque and temperature; a misrouted oil feed shows up in the first minutes of running.
Typical equipment & failure modes
Common applications
- bulk-handler stacker/reclaimer slew pivots
- vertical hydro-turbine and large pump thrust supports
- rolling-mill screwdown and backup-roll thrust positions
- large crane and excavator slew thrust rings
Known failure patterns
- cage and roller-end scoring when the shaft was forced into alignment by the bearing itself during a bent-shaft rescue
- roller/raceway scuffing from an interrupted oil supply — at these loads the EHL film is the only thing between rolling and smearing
- flaking that started where radial load share grew past the design assumption — the bearing tolerates combined load only while axial load clearly dominates
- cage-pocket wear after long service with vibration at standstill, the rollers hammering the pocket surfaces
- fatigue spalling on the shaft-washer raceway beginning at the high-stress inner end of the roller contact
Selection pitfalls — read before you substitute
- Bearings of 90 mm bore need planned lifting and heating; a shaft washer driven on cold and crooked starts the failure clock before the first load.
- The 293 medium section is the workhorse: balanced height and capacity for general heavy thrust duty at 90 mm bore.
- Mixing washers between bearings during overhaul is a real risk at this size — rollers and raceways run in together, so keep each 29318 stack as a set.
- Axial load must dominate; letting the radial share creep up because the radial bearing wore is the quiet path to early raceway flaking.
- Do not let the self-aligning travel absorb a bent shaft: the bearing aligns to seats, not to a shaft that whips.
- The Ca 320/C0a 915 kN ratings and 84 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 29318; roller profile and osculation legitimately differ between manufacturers, so re-verify ratings, oil supply and minimum load before substituting another make.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 29318?
29318 is a spherical roller thrust bearing to ISO 104: 90 mm shaft-washer bore, 155 mm outside diameter, 39 mm stack height (3.543 x 6.102 x 1.535 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 320 kN, C0a 915 kN and a 84 kN fatigue load limit Pu; limiting speed 2,300 r/min with oil lubrication; mass about 3080 g.
How is the 29318 designation structured?
293 is the dimension series (medium-section 29300 spherical-thrust family); 18 encodes the 90 mm bore (bore code x 5). The 155 mm OD and 39 mm height follow the ISO 104 boundary plan for that series.
Can 29318 handle misalignment and radial load?
Yes to both, with limits. The spherical housing-washer raceway lets the bearing self-align against steady seat misalignment, and the angled roller contact tolerates a radial share while axial load clearly dominates. It is not a radial bearing: shaft radial location still needs its own radial bearing.
Why does NTN print only an oil speed, 2,300 r/min, for 29318?
Spherical roller thrust bearings of this size work under contact stresses that need an elastohydrodynamic oil film; grease is reserved for the smallest, slowest duties. The printed figure is the limiting speed with the catalogue oil-lubrication state — bath level, viscosity and cooling decide how close a real installation may run.
What should be checked before substituting another make for 29318?
The 90/155/39 mm envelope is ISO 104 interchangeable, but roller profile, osculation, cage and washer details are maker-specific. Re-verify Ca 320 kN / C0a 915 kN, the oil speed rating and the minimum-load requirement against the donor catalogue before swapping on a rated drive.
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.