51172 bearing: complete specifications & equivalents
The 51172 is a ISO 104 radial bearing sized 360 x 440 x 65 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 360 mm |
| Outer diameter D | 440 mm |
| Width B | 65 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 380 kN |
| Basic static load rating C0 | 1860 kN |
| Fatigue load limit Pu | 42 kN |
| Limiting speed (mechanical) | 510 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 21100 g |
| Manufacturer designation | NTN 51172 |
| 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 & 51100-series range
| Bore d | 14.173 in |
|---|---|
| Outer diameter D | 17.323 in |
| Width B | 2.559 in |
| ISO bore code | 72 |
| Radial section height (D−d)/2 | 40 mm |
| Smallest bore in 51100-series | 10 mm |
| Largest outer diameter in 51100-series | 640 mm |
| Width range across 51100-series | 9–85 mm |
| Bore position in 51100-series (smallest first) | 38 of 46 |
| Bore above smallest 51100-series size | 350 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 51172 model number is decoded
51172 is the 360 mm member of NTN's light-section 51100 thrust family: 440 mm across the washers, 65 mm tall. Reading the code: 511 is the dimension series (light-section 51100 thrust family), and 72 encodes the 360 mm bore (bore code x 5). The washer section here is 40.0 mm of radial height, and the catalogue couples it with Ca 380 kN / C0a 1860 kN. Choose the light-section 51100 thrust family when the shaft carries pure thrust in one direction at moderate speed — vertical shafts are the textbook case. Preload or working clearance must guarantee the minimum axial load at the catalogue speed; a spring or dead-weight arrangement is the usual answer on high-speed vertical shafts.
Typical equipment & failure modes
Common applications
- vertical hydro and pump-turbine thrust supports
- large marine winch and windlass shafts
- heavy press and mill screwdown thrust seats
- crane slew-ring auxiliary thrust positions
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
- contamination pitting from particles settling on the horizontal housing washer — the classic failure of vertical-shaft grease-lubricated seats
- 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 360 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 511 light section is the speed-friendly end of the thrust-ball plan — for the same 360 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Radial load is the silent killer here: a belt pull or gear force on the same shaft must land on a radial bearing, because 51172 has no radial capacity at all.
- Shock thrust above C0a 1860 kN leaves dents that later become fatigue origins — crane-hook and press applications need the static check, not just the life calculation.
- The C0a of 1860 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- The Ca 380/C0a 1860 kN ratings and 42 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51172; 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 51172?
51172 is a single-direction thrust ball bearing to ISO 104: 360 mm shaft-washer bore, 440 mm outside diameter, 65 mm stack height (14.173 x 17.323 x 2.559 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 380 kN, C0a 1860 kN and a 42 kN fatigue load limit Pu; the grease limiting speed is 510 r/min and the oil rating 730 r/min; mass about 21100 g.
How is the 51172 designation structured?
511 is the dimension series (light-section 51100 thrust family); 72 encodes the 360 mm bore (bore code x 5). The 440 mm OD and 65 mm height follow the ISO 104 boundary plan for that series.
Can 51172 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 51172?
At the 510 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 51172?
The 360/440/65 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 380 kN / C0a 1860 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.