51236 bearing: complete specifications & equivalents
The 51236 is a ISO 104 radial bearing sized 180 x 250 x 56 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 180 mm |
| Outer diameter D | 250 mm |
| Width B | 56 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 266 kN |
| Basic static load rating C0 | 875 kN |
| Fatigue load limit Pu | 26.9 kN |
| Limiting speed (mechanical) | 780 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 8340 g |
| Manufacturer designation | NTN 51236 |
| 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 | 7.087 in |
|---|---|
| Outer diameter D | 9.843 in |
| Width B | 2.205 in |
| ISO bore code | 36 |
| Radial section height (D−d)/2 | 35 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) | 28 of 39 |
| Bore above smallest 51200-series size | 170 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51236 model number is decoded
From the medium-section 51200 thrust family, 51236 measures 180 mm through the shaft washer, 250 mm over the outside and 56 mm in assembled height. Reading the code: 512 is the dimension series (medium-section 51200 thrust family), and 36 encodes the 180 mm bore (bore code x 5). The static margin, C0a 875 kN against Ca 266 kN, is what carries slow oscillating or shock thrust without permanent raceway dents. Against a thrust roller bearing of the same 180 mm bore, this bearing is cheaper, quieter and happier at speed, but carries far less load per mm of section. Keep the support faces square: a housing face out of perpendicular by a few hundredths over the 250 mm OD already tilts the raceway and concentrates the 875 kN static capacity on a few balls.
Typical equipment & failure modes
Common applications
- crane slew-ring auxiliary thrust positions
- large mixer and reactor vertical shafts
- bulk-handler stacker/reclaimer thrust pivots
- heavy rotary furnace and kiln thrust points
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
- washer face corrosion under long standstill in humid service, later printed into the raceway as evenly spaced pitting
- 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
- For a 180 mm bore thrust bearing, the seating surfaces and oil supply decide service life; at this size a field-improvised housing is the usual root cause behind "premature" failures.
- The 512 medium section is the default choice: balanced height and capacity for general vertical-shaft duty at 180 mm bore.
- Shock thrust above C0a 875 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- A housing washer pressed tight in its seat cannot self-centre; the resulting eccentric running shows up as cage wear long before raceway fatigue.
- Shock thrust above C0a 875 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The Ca 266/C0a 875 kN ratings and 26.9 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51236; 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 51236?
51236 is a single-direction thrust ball bearing to ISO 104: 180 mm shaft-washer bore, 250 mm outside diameter, 56 mm stack height (7.087 x 9.843 x 2.205 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 266 kN, C0a 875 kN and a 26.9 kN fatigue load limit Pu; the grease limiting speed is 780 r/min and the oil rating 1,100 r/min; mass about 8340 g.
How is the 51236 designation structured?
512 is the dimension series (medium-section 51200 thrust family); 36 encodes the 180 mm bore (bore code x 5). The 250 mm OD and 56 mm height follow the ISO 104 boundary plan for that series.
Can 51236 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 51236?
At the 780 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 51236?
The 180/250/56 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 266 kN / C0a 875 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.