51109 bearing: complete specifications & equivalents
The 51109 is a ISO 104 radial bearing sized 45 x 65 x 14 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 45 mm |
| Outer diameter D | 65 mm |
| Width B | 14 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Basic dynamic load rating C | 27.9 kN |
| Basic static load rating C0 | 69 kN |
| Fatigue load limit Pu | 3.1 kN |
| Limiting speed (mechanical) | 3200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 148 g |
| Manufacturer designation | NTN 51109 |
| 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 | 1.772 in |
|---|---|
| Outer diameter D | 2.559 in |
| Width B | 0.551 in |
| ISO bore code | 09 |
| Radial section height (D−d)/2 | 10 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) | 10 of 46 |
| Bore above smallest 51100-series size | 35 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 51109-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 51109 model number is decoded
51109 is the 45 mm member of NTN's light-section 51100 thrust family: 65 mm across the washers, 14 mm tall. NTN builds the number from 511 is the dimension series (light-section 51100 thrust family); 09 encodes the 45 mm bore (bore code x 5). The washer section here is 10.0 mm of radial height, and the catalogue couples it with Ca 27.9 kN / C0a 69 kN. The 45/65/14 envelope follows ISO 104, so dimensional interchange holds between makers — raceway osculation and ratings do not automatically follow. 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
- machine-tool tailstock and steady-rest screws
- medium crane hook blocks and slewing jibs
- extruder and mixer thrust housings
- winch and capstan vertical shafts
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
- 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
- lubricant starvation scoring on the raceway track when grease is thrown outward by centrifugal effect and never replaced
Selection pitfalls — read before you substitute
- In this size class the frequent miss is washer identification: keep the catalogued shaft/housing washer pairing of the 45 mm size together from unpacking to assembly.
- The 511 light section is the speed-friendly end of the thrust-ball plan — for the same 45 mm bore it gives up load to gain OD, height and limiting-speed headroom.
- Swapping the shaft and housing washers is an easy assembly error on the 45 mm size — the bores differ only slightly, but the wrong pairing walks off-centre under load.
- Single-direction means exactly that: thrust on 51109 in the wrong direction separates the washers and drops the ball set — if reversal is possible even during coast-down, engineer against it.
- The C0a of 69 kN is a static rating: sizing continuous working thrust from C0a alone overstates what the raceway survives.
- The Ca 27.9/C0a 69 kN ratings and 3.1 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 51109; 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 51109?
51109 is a single-direction thrust ball bearing to ISO 104: 45 mm shaft-washer bore, 65 mm outside diameter, 14 mm stack height (1.772 x 2.559 x 0.551 in). From NTN Ball and Roller Bearings CAT.No.2203E: axial Ca 27.9 kN, C0a 69 kN and a 3.1 kN fatigue load limit Pu; the grease limiting speed is 3,200 r/min and the oil rating 4,600 r/min; mass about 148 g.
How is the 51109 designation structured?
511 is the dimension series (light-section 51100 thrust family); 09 encodes the 45 mm bore (bore code x 5). The 65 mm OD and 14 mm height follow the ISO 104 boundary plan for that series.
Can 51109 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 51109?
At the 3,200 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 51109?
The 45/65/14 mm envelope is ISO 104 interchangeable, but washer bore codes, raceway osculation and ratings are maker-specific. Re-verify Ca 27.9 kN / C0a 69 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.