51206 bearing: complete specifications & equivalents
The 51206 is a ISO 104 radial bearing sized 30 x 52 x 16 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 | 52 mm |
| Width B | 16 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 29.3 kN |
| Basic static load rating C0 | 58 kN |
| Fatigue load limit Pu | 2.63 kN |
| Limiting speed (mechanical) | 3400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 139 g |
| Manufacturer designation | NTN 51206 |
| 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 & 51200-series range
| Bore d | 1.181 in |
|---|---|
| Outer diameter D | 2.047 in |
| Width B | 0.63 in |
| ISO bore code | 06 |
| Radial section height (D−d)/2 | 11 mm |
| Smallest bore in 51200-series | 10 mm |
| Largest outer diameter in 51200-series | 520 mm |
| Width range across 51200-series | 11–112 mm |
| Bore position in 51200-series (smallest first) | 7 of 39 |
| Bore above smallest 51200-series size | 20 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51206-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 30×52×16 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 51206 model number is decoded
At 30 x 52 x 16 mm, NTN 51206 sits in the medium-section 51200 thrust family of the single-direction thrust programme. The designation is 512 is the dimension series (medium-section 51200 thrust family) plus 06 encodes the 30 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. The 30/52/16 envelope follows ISO 104, so dimensional interchange holds between makers — raceway osculation and ratings do not automatically follow. On a vertical shaft, pack grease between the washers and plan a relubrication path — centrifugal effect drives grease outward and the track runs dry without it.
Typical equipment & failure modes
Common applications
- vertical motor and pump thrust shoes
- machine-tool tailstock and steady-rest screws
- medium crane hook blocks and slewing jibs
- extruder and mixer thrust housings
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
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
- 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
- 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 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 30 mm bore.
- 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 51206 stack height of 16 mm and washer set differ from the double-direction execution.
- Single-direction means exactly that: thrust on 51206 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 29.3/C0a 58 kN ratings and 2.63 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51206; 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 51206?
51206 is a single-direction thrust ball bearing to ISO 104: 30 mm shaft-washer bore, 52 mm outside diameter, 16 mm stack height (1.181 x 2.047 x 0.63 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 29.3 kN, C0a 58 kN and a 2.63 kN fatigue load limit Pu; the grease limiting speed is 3,400 r/min and the oil rating 4,900 r/min; mass about 139 g.
How is the 51206 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 06 encodes the 30 mm bore (bore code x 5). The 52 mm OD and 16 mm height follow the ISO 104 boundary plan for that series.
Can 51206 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 51206?
At the 3,400 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 51206?
The 30/52/16 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 29.3 kN / C0a 58 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.