51201 bearing: complete specifications & equivalents
The 51201 is a ISO 104 radial bearing sized 12 x 28 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 | 12 mm |
| Outer diameter D | 28 mm |
| Width B | 11 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 13.2 kN |
| Basic static load rating C0 | 19 kN |
| Fatigue load limit Pu | 0.86 kN |
| Limiting speed (mechanical) | 5600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 34 g |
| Manufacturer designation | NTN 51201 |
| 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 | 0.472 in |
|---|---|
| Outer diameter D | 1.102 in |
| Width B | 0.433 in |
| ISO bore code | 01 |
| Radial section height (D−d)/2 | 8 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) | 2 of 39 |
| Bore above smallest 51200-series size | 2 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51201-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 51201 model number is decoded
From the medium-section 51200 thrust family, 51201 measures 12 mm through the shaft washer, 28 mm over the outside and 11 mm in assembled height. The designation is 512 is the dimension series (medium-section 51200 thrust family) plus the bore code 01 maps to the 12 mm bore by the standard table. The static margin, C0a 19 kN against Ca 13.2 kN, is what carries slow oscillating or shock thrust without permanent raceway dents. If the duty is high speed with light thrust, check the minimum axial load formula first; a too-large thrust ball bearing fails by skid long before its Ca of 13.2 kN is ever approached. 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
- valve actuator and gearbox thrust seats
- food-machine vertical auger shafts
- laboratory centrifuge and mixer thrust ends
- small vertical pump and agitator thrust positions
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
- early fatigue from thrust reversal hammering the unloaded raceway, because the bearing has no contact surfaces for the opposite direction
- 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
- Small thrust washers of 12 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 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 12 mm bore.
- The 5,600 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 C0a of 19 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- Shock thrust above C0a 19 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The Ca 13.2/C0a 19 kN ratings and 0.86 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51201; 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 51201?
51201 is a single-direction thrust ball bearing to ISO 104: 12 mm shaft-washer bore, 28 mm outside diameter, 11 mm stack height (0.472 x 1.102 x 0.433 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 13.2 kN, C0a 19 kN and a 0.86 kN fatigue load limit Pu; the grease limiting speed is 5,600 r/min and the oil rating 8,000 r/min; mass about 34 g.
How is the 51201 designation structured?
512 is the dimension series (medium-section 51200 thrust family); the bore code 01 maps to the 12 mm bore by the standard table. The 28 mm OD and 11 mm height follow the ISO 104 boundary plan for that series.
Can 51201 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 51201?
At the 5,600 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 51201?
The 12/28/11 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 13.2 kN / C0a 19 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.