51338 bearing: complete specifications & equivalents
The 51338 is a ISO 104 radial bearing sized 190 x 320 x 105 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 190 mm |
| Outer diameter D | 320 mm |
| Width B | 105 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 545 kN |
| Basic static load rating C0 | 1950 kN |
| Fatigue load limit Pu | 55 kN |
| Limiting speed (mechanical) | 500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 35000 g |
| Manufacturer designation | NTN 51338 |
| 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 & 51300-series range
| Bore d | 7.48 in |
|---|---|
| Outer diameter D | 12.598 in |
| Width B | 4.134 in |
| ISO bore code | 38 |
| Radial section height (D−d)/2 | 65 mm |
| Smallest bore in 51300-series | 25 mm |
| Largest outer diameter in 51300-series | 340 mm |
| Width range across 51300-series | 18–110 mm |
| Bore position in 51300-series (smallest first) | 24 of 25 |
| Bore above smallest 51300-series size | 165 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51338-M | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 190×320×105 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 51338 model number is decoded
The heavy-section 51300 thrust family entry 51338 stacks a shaft washer, ball-and-cage set and housing washer into 105 mm of height over a 190 mm bore. Two fields make up the code — 513 is the dimension series (heavy-section 51300 thrust family) and 38 encodes the 190 mm bore (bore code x 5). Because the contact points run at 90 deg to the shaft, none of the rating is available for radial load — not even incidentally. Against a thrust roller bearing of the same 190 mm bore, this bearing is cheaper, quieter and happier at speed, but carries far less load per mm of section. Mount the stack in order and confirm the shaft washer sits against its shoulder before loading: pressing through the balls brinells the raceway on the spot.
Typical equipment & failure modes
Common applications
- heavy rotary furnace and kiln thrust points
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
Known failure patterns
- cage pocket wear and ball skid polish after long running below the minimum axial load, the balls sliding instead of rolling on the washers
- housing-washer rocking on an out-of-square support face, seen as uneven wear around the raceway circle and rising running torque
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
Selection pitfalls — read before you substitute
- For a 190 mm bore thrust bearing, the seating surfaces and oil supply decide service life; at this size a field-improvised housing is the usual root cause behind "premature" failures.
- The 513 heavy section buys capacity with a larger 320 mm OD and taller stack — check the housing space before upgrading a 512 position to this series.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51338 has no radial capacity at all.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51338 stack height of 105 mm and washer set differ from the double-direction execution.
- Single-direction means exactly that: thrust on 51338 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- The Ca 545/C0a 1950 kN ratings and 55 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51338; raceway geometry legitimately differs between manufacturers, so re-verify ratings and washer identification before substituting another make.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 51338?
51338 is a single-direction thrust ball bearing to ISO 104: 190 mm shaft-washer bore, 320 mm outside diameter, 105 mm stack height (7.48 x 12.598 x 4.134 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 545 kN, C0a 1950 kN and a 55 kN fatigue load limit Pu; the grease limiting speed is 500 r/min and the oil rating 710 r/min; mass about 35000 g.
How is the 51338 designation structured?
513 is the dimension series (heavy-section 51300 thrust family); 38 encodes the 190 mm bore (bore code x 5). The 320 mm OD and 105 mm height follow the ISO 104 boundary plan for that series.
Can 51338 carry radial load or reversing thrust?
No. The raceways contact the balls at 90 deg to the shaft, so the rating is purely axial and single-direction. Radial load must be carried by a separate radial bearing, and reversing thrust needs a second thrust bearing or a double-direction execution.
Why does NTN specify a minimum axial load for 51338?
At the 500 r/min class speed, centrifugal and gyroscopic effects make an under-loaded ball set skid and smear instead of roll. The catalogue minimum-load formula gives the axial preload — from the machine weight, springs or a dead-weight — that keeps the contact rolling.
What should be checked before substituting another make for 51338?
The 190/320/105 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 545 kN / C0a 1950 kN, the speed figures and the shaft/housing washer identification against the donor catalogue.
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.