51216 bearing: complete specifications & equivalents
The 51216 is a ISO 104 radial bearing sized 80 x 115 x 28 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 80 mm |
| Outer diameter D | 115 mm |
| Width B | 28 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 78.5 kN |
| Basic static load rating C0 | 218 kN |
| Fatigue load limit Pu | 9.85 kN |
| Limiting speed (mechanical) | 1700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 916 g |
| Manufacturer designation | NTN 51216 |
| 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 | 3.15 in |
|---|---|
| Outer diameter D | 4.528 in |
| Width B | 1.102 in |
| ISO bore code | 16 |
| Radial section height (D−d)/2 | 17.5 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) | 17 of 39 |
| Bore above smallest 51200-series size | 70 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51216-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 51216 model number is decoded
51216 is an NTN single-direction thrust ball bearing of the medium-section 51200 thrust family: 80 mm bore, 115 mm outside diameter, 28 mm overall height in NTN Ball and Roller Bearings CAT.No.2203E. Two fields make up the code — 512 is the dimension series (medium-section 51200 thrust family) and 16 encodes the 80 mm bore (bore code x 5). Catalogue axial dynamic rating Ca is 78.5 kN against C0a 218 kN — a static/dynamic ratio of 2.78 that is the signature of a thrust raceway. 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 78.5 kN is ever approached. Mount the stack in order and confirm the shaft washer sits against its shoulder before loading: pressing through the balls brinells the raceway on the spot.
Typical equipment & failure modes
Common applications
- large crane hook and swivel assemblies
- rolling-mill screwdown and adjustment screws
- heavy press and forging-machine thrust seats
- ship winch and capstan thrust shafts
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
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
- cage breakage after repeated shock reversal banged the ball set against the pocket bridges
Selection pitfalls — read before you substitute
- At 80 mm bore the washers are heavy enough to sag out of square during assembly — support the stack horizontally where possible and verify face runout before loading.
- The 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 80 mm bore.
- Grease in a horizontal-washer seat stays only if the housing is designed to hold it; open vertical arrangements need an oil bath or a grease-retaining cover.
- Shock thrust above C0a 218 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- Swapping the shaft and housing washers is an easy assembly error on the 80 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- The Ca 78.5/C0a 218 kN ratings and 9.85 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51216; 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 51216?
51216 is a single-direction thrust ball bearing to ISO 104: 80 mm shaft-washer bore, 115 mm outside diameter, 28 mm stack height (3.15 x 4.528 x 1.102 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 78.5 kN, C0a 218 kN and a 9.85 kN fatigue load limit Pu; the grease limiting speed is 1,700 r/min and the oil rating 2,400 r/min; mass about 916 g.
How is the 51216 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 16 encodes the 80 mm bore (bore code x 5). The 115 mm OD and 28 mm height follow the ISO 104 boundary plan for that series.
Can 51216 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 51216?
At the 1,700 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 51216?
The 80/115/28 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 78.5 kN / C0a 218 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.