51138 bearing: complete specifications & equivalents
The 51138 is a ISO 104 radial bearing sized 190 x 240 x 37 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 | 240 mm |
| Width B | 37 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 170 kN |
| Basic static load rating C0 | 655 kN |
| Fatigue load limit Pu | 20.2 kN |
| Limiting speed (mechanical) | 980 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3750 g |
| Manufacturer designation | NTN 51138 |
| 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 & 51100-series range
| Bore d | 7.48 in |
|---|---|
| Outer diameter D | 9.449 in |
| Width B | 1.457 in |
| ISO bore code | 38 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 51100-series | 10 mm |
| Largest outer diameter in 51100-series | 640 mm |
| Width range across 51100-series | 9–85 mm |
| Bore position in 51100-series (smallest first) | 29 of 46 |
| Bore above smallest 51100-series size | 180 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51138 model number is decoded
From the light-section 51100 thrust family, 51138 measures 190 mm through the shaft washer, 240 mm over the outside and 37 mm in assembled height. NTN builds the number from 511 is the dimension series (light-section 51100 thrust family); 38 encodes the 190 mm bore (bore code x 5). On speed, the grease limiting speed is 980 r/min and the oil rating 1,400 r/min. For a 190 mm shaft with combined radial-plus-axial load, pair this bearing with a separate radial bearing — the thrust ball bearing must never be asked to carry the radial share. The housing washer needs radial freedom in its seat so the bearing can centre itself; clamping it radially defeats the self-centring the loose fit is designed to give.
Typical equipment & failure modes
Common applications
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
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
- early fatigue from thrust reversal hammering the unloaded raceway, because the bearing has no contact surfaces for the opposite direction
- edge loading from a shaft washer mounted off-centre, cutting the contact ellipse short at one side of the track
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
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 511 light section is the speed-friendly end of the thrust-ball plan — for the same 190 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Swapping the shaft and housing washers is an easy assembly error on the 190 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- The Ca 170/C0a 655 kN ratings and 20.2 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51138; 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 51138?
51138 is a single-direction thrust ball bearing to ISO 104: 190 mm shaft-washer bore, 240 mm outside diameter, 37 mm stack height (7.48 x 9.449 x 1.457 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 170 kN, C0a 655 kN and a 20.2 kN fatigue load limit Pu; the grease limiting speed is 980 r/min and the oil rating 1,400 r/min; mass about 3750 g.
How is the 51138 designation structured?
511 is the dimension series (light-section 51100 thrust family); 38 encodes the 190 mm bore (bore code x 5). The 240 mm OD and 37 mm height follow the ISO 104 boundary plan for that series.
Can 51138 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 51138?
At the 980 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 51138?
The 190/240/37 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 170 kN / C0a 655 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.