51106 bearing: complete specifications & equivalents
The 51106 is a ISO 104 radial bearing sized 30 x 47 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 | 30 mm |
| Outer diameter D | 47 mm |
| Width B | 11 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 20.4 kN |
| Basic static load rating C0 | 42 kN |
| Fatigue load limit Pu | 1.9 kN |
| Limiting speed (mechanical) | 4300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 69 g |
| Manufacturer designation | NTN 51106 |
| 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 | 1.181 in |
|---|---|
| Outer diameter D | 1.85 in |
| Width B | 0.433 in |
| ISO bore code | 06 |
| 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) | 7 of 46 |
| Bore above smallest 51100-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51106-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 51106 model number is decoded
NTN 51106 belongs to the light-section 51100 thrust family of single-direction thrust ball bearings: 30 / 47 / 11 mm (shaft bore / OD / height). Reading the code: 511 is the dimension series (light-section 51100 thrust family), and 06 encodes the 30 mm bore (bore code x 5). NTN prints 20.4 kN axial dynamic and 42 kN axial static for this size and a 1.9 kN fatigue load limit Pu. Within the thrust-ball plan, 511 is the light section and 514 the heaviest for a given bore; moving up a series raises the C0a from 42 kN class figures at the cost of OD and height. Preload or working clearance must guarantee the minimum axial load at the catalogue speed; a spring or dead-weight arrangement is the usual answer on high-speed vertical shafts.
Typical equipment & failure modes
Common applications
- medium crane hook blocks and slewing jibs
- extruder and mixer thrust housings
- winch and capstan vertical shafts
- press and punch-machine thrust seats
Known failure patterns
- ball and raceway smearing from gyroscopic spin when the bearing runs fast under too little axial load — the minimum-load rule exists exactly for this
- fretting between shaft washer and shaft when the seat is cut loose — the washer creeps, the centre line shifts and the balls start running off-track
- rapid flaking after radial load was allowed onto the bearing — a single-direction thrust ball bearing carries axial load only
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
- edge loading from a shaft washer mounted off-centre, cutting the contact ellipse short at one side of the track
Selection pitfalls — read before you substitute
- In this size class the frequent miss is washer identification: keep the catalogued shaft/housing washer pairing of the 30 mm size together from unpacking to assembly.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 30 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- The 4,300 r/min speed figure assumes the catalogue lubrication state; at high speed the limiting factor is often the minimum load, not the rating table.
- The 4,300 r/min speed figure assumes the catalogue lubrication state; at high speed the limiting factor is often the minimum load, not the rating table.
- 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.
- The Ca 20.4/C0a 42 kN ratings and 1.9 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51106; 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 51106?
51106 is a single-direction thrust ball bearing to ISO 104: 30 mm shaft-washer bore, 47 mm outside diameter, 11 mm stack height (1.181 x 1.85 x 0.433 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 20.4 kN, C0a 42 kN and a 1.9 kN fatigue load limit Pu; the grease limiting speed is 4,300 r/min and the oil rating 6,200 r/min; mass about 69 g.
How is the 51106 designation structured?
511 is the dimension series (light-section 51100 thrust family); 06 encodes the 30 mm bore (bore code x 5). The 47 mm OD and 11 mm height follow the ISO 104 boundary plan for that series.
Can 51106 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 51106?
At the 4,300 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 51106?
The 30/47/11 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 20.4 kN / C0a 42 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.