51220 bearing: complete specifications & equivalents
The 51220 is a ISO 104 radial bearing sized 100 x 150 x 38 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 100 mm |
| Outer diameter D | 150 mm |
| Width B | 38 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 147 kN |
| Basic static load rating C0 | 410 kN |
| Fatigue load limit Pu | 16.6 kN |
| Limiting speed (mechanical) | 1300 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2290 g |
| Manufacturer designation | NTN 51220 |
| 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 | 3.937 in |
|---|---|
| Outer diameter D | 5.906 in |
| Width B | 1.496 in |
| ISO bore code | 20 |
| Radial section height (D−d)/2 | 25 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) | 20 of 39 |
| Bore above smallest 51200-series size | 90 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51220-SKF | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 100×150×38 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 51220 model number is decoded
At 100 x 150 x 38 mm, NTN 51220 sits in the medium-section 51200 thrust family of the single-direction thrust programme. Decoding 51220: 512 is the dimension series (medium-section 51200 thrust family), with 20 encodes the 100 mm bore (bore code x 5). Catalogue mass is about 2290 g for the full washer-and-cage stack. For a 100 mm shaft with combined radial-plus-axial load, pair this bearing with a separate radial bearing — the thrust ball bearing must never be asked to carry the radial share. 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
- ship winch and capstan thrust shafts
- crusher main-shaft thrust supports
- large rotary-table and index-table thrust rings
- vertical water-pump and turbine thrust blocks
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
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
Selection pitfalls — read before you substitute
- At 100 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 100 mm bore.
- Single-direction means exactly that: thrust on 51220 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- Below the minimum axial load the balls skid; the catalogue Ca of 147 kN never saves a bearing that is running too lightly loaded at 1,300 r/min.
- The 1,300 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 Ca 147/C0a 410 kN ratings and 16.6 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51220; 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 51220?
51220 is a single-direction thrust ball bearing to ISO 104: 100 mm shaft-washer bore, 150 mm outside diameter, 38 mm stack height (3.937 x 5.906 x 1.496 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 147 kN, C0a 410 kN and a 16.6 kN fatigue load limit Pu; the grease limiting speed is 1,300 r/min and the oil rating 1,800 r/min; mass about 2290 g.
How is the 51220 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 20 encodes the 100 mm bore (bore code x 5). The 150 mm OD and 38 mm height follow the ISO 104 boundary plan for that series.
Can 51220 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 51220?
At the 1,300 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 51220?
The 100/150/38 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 147 kN / C0a 410 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.