51105 bearing: complete specifications & equivalents
The 51105 is a ISO 104 radial bearing sized 25 x 42 x 11 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 25 mm |
| Outer diameter D | 42 mm |
| Width B | 11 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 19.6 kN |
| Basic static load rating C0 | 37 kN |
| Fatigue load limit Pu | 1.68 kN |
| Limiting speed (mechanical) | 4600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 60 g |
| Manufacturer designation | NTN 51105 |
| 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 | 0.984 in |
|---|---|
| Outer diameter D | 1.654 in |
| Width B | 0.433 in |
| ISO bore code | 05 |
| Radial section height (D−d)/2 | 8.5 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) | 6 of 46 |
| Bore above smallest 51100-series size | 15 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51105-SKF | SKF | full Dimensions and internal design equivalent — standard interchange. | Identical ISO 15 envelope, seal and ratings band — standard interchange; re-verify precision class and clearance per supplier. |
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 51105 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 51105 appears as a light-section 51100 thrust family bearing with a 25 mm shaft washer, a 42 mm housing diameter and 11 mm of stack height. The designation is 511 is the dimension series (light-section 51100 thrust family) plus 05 encodes the 25 mm bore (bore code x 5). Flat-seat washers make the bearing tolerant of simple housings but demand square faces: the whole 19.6 kN rating assumes the load arrives truly axial. Size selection ends with the minimum-load check: at the 4,600 r/min class speed, the balls need a defined axial preload to keep rolling instead of skidding. 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
- small vertical pump and agitator thrust positions
- bench drill-press and tapping-machine spindles
- automotive steering-gear and clutch release points
- small crane hook and swivel-joint thrust supports
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
- contamination pitting from particles settling on the horizontal housing washer — the classic failure of vertical-shaft grease-lubricated seats
Selection pitfalls — read before you substitute
- Small thrust washers of 25 mm bore bend if the shaft shoulder is rough — check burrs before seating, and never press on the housing washer to drive the shaft washer home.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 25 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Do not reuse a thrust bearing to "absorb" shaft thermal growth — the bearing clamps axially, so growth must be handled on the radial-bearing side of the arrangement.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- Never substitute a double-direction bearing drawing part-for-part: the single-direction 51105 stack height of 11 mm and washer set differ from the double-direction execution.
- The Ca 19.6/C0a 37 kN ratings and 1.68 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51105; 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 51105?
51105 is a single-direction thrust ball bearing to ISO 104: 25 mm shaft-washer bore, 42 mm outside diameter, 11 mm stack height (0.984 x 1.654 x 0.433 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 19.6 kN, C0a 37 kN and a 1.68 kN fatigue load limit Pu; the grease limiting speed is 4,600 r/min and the oil rating 6,500 r/min; mass about 60 g.
How is the 51105 designation structured?
511 is the dimension series (light-section 51100 thrust family); 05 encodes the 25 mm bore (bore code x 5). The 42 mm OD and 11 mm height follow the ISO 104 boundary plan for that series.
Can 51105 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 51105?
At the 4,600 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 51105?
The 25/42/11 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 19.6 kN / C0a 37 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.