A spherical roller thrust bearing looks like a spherical roller bearing that's been laid on its side. It hasn't — it's a different bearing family, built specifically to carry heavy axial load in one direction, with the ability to take some radial load and some shaft misalignment on top of it.
If your application is a vertical pump shaft, a crane hook, a screw press, or a ship's propulsion thrust — anything where the dominant load pushes along the shaft rather than across it — this is very likely the bearing already sitting in that position.
How It's Built
The bearing has two main rings — a shaft washer (the bore-side ring, mounted on the rotating shaft) and a housing washer (the larger ring, with a spherical raceway). Between them sits a single row of asymmetric rollers held in a cage, arranged around a contact angle of approximately 45°.
That spherical housing washer raceway is the entire reason this bearing can self-align. The center of the sphere sits on the bearing axis, so the housing washer can rock relative to the shaft washer without changing the load path through the rollers. This absorbs shaft deflection or housing misalignment that would bind a flat thrust bearing.
The 45° contact angle is what lets the bearing carry radial load alongside its primary axial load — but only up to a point. Radial load must not exceed 55% of the axial load. Push past that ratio and the bearing is being asked to do a cylindrical roller bearing's job with the wrong geometry for it; life drops sharply.
Tight Ring vs. Loose Ring — A Detail Unique to This Bearing
Unlike a standard spherical roller bearing, a spherical roller thrust bearing has two rings that are deliberately different sizes — the bore diameter difference between them typically runs 0.1–0.5 mm. One ring is the tight ring (interference-fit to the rotating shaft) and one is the loose ring (free to seat against a stationary face).
Getting this backward during installation — mounting the loose ring where the tight ring belongs — is a mounting error specific to this bearing type, and it's worth checking with a bore gauge before pressing anything into place, since the two rings can otherwise look identical. The loose ring must always rest against the stationary member of the assembly, not against a rotating part.
Size and Load Range (29300 Series)
The 29300 series is the standard single-direction spherical roller thrust bearing range. Load capacity scales steeply with bore size — moving from a 180 mm bore to a 300 mm bore more than doubles the dynamic load rating:
Designation | Bore (mm) | OD (mm) | Width (mm) | Dynamic Load (N) | Static Load (N) | Max Speed (rpm) |
|---|---|---|---|---|---|---|
29336 | 180 | 300 | 73 | 1,020,000 | 3,950,000 | 2,000 |
29340 | 200 | 340 | 85 | 1,350,000 | 5,250,000 | 1,700 |
29360 | 300 | 480 | 109 | 2,310,000 | 10,000,000 | 1,200 |
Two things stand out reading across this table. First, the static load rating is consistently 3–4x the dynamic rating — a signature of a bearing designed to sit under heavy, largely stationary load (a parked vertical pump shaft, a loaded crane hook) as often as it runs.
Second, maximum speed drops fast as bore increases; the 300 mm-bore 29360 is rated for only about 60% of the rpm of the 180 mm-bore 29336. This bearing family trades speed for load capacity by design — it is not the right choice for a high-speed thrust position.
Where It's Actually Used
Vertical pump shafts — the entire rotor weight plus pumping thrust load downward through a single bearing at the bottom of the shaft.
Crane hook blocks and hoist mechanisms — pure axial load from the suspended weight, often at very low or intermittent speed.
Extruder and screw press shafts — high, steady axial thrust from the screw pushing against material resistance.
Ship propulsion thrust blocks — propeller thrust transmitted through a low-speed, high-load shaft.
Rolling mill and heavy machine tool spindles — where axial cutting or rolling force needs a bearing that also tolerates some shaft deflection under load.
Spherical Roller Thrust Bearing vs. Standard Spherical Roller Bearing
A standard (radial) spherical roller bearing carries radial load as its primary function and can accept some axial load in both directions. A spherical roller thrust bearing inverts that: axial load in one direction only is primary, and radial load is the secondary, limited capacity. They are not interchangeable positions in a shaft arrangement — a radial SRB used where a thrust SRB belongs will be overloaded axially long before it reaches its radial fatigue life, and vice versa.
For the dimensions and load ratings of the radial series, see our spherical roller bearing size chart.
FAQ
Can a spherical roller thrust bearing take load in both axial directions?
No — the 29300 series is single-direction by design. An application with axial load reversing direction (rare for the applications this bearing is used in) needs a different bearing arrangement, typically two thrust bearings back to back with a spacer, or a different bearing type entirely.
Does misalignment tolerance mean the shaft can be installed slightly out of square?
The self-aligning capability compensates for shaft deflection and minor housing misalignment that occurs under load or from manufacturing tolerance — it is not a substitute for correct initial alignment during installation. Treating it as forgiving of poor alignment from the outset shortens roller and raceway life.
What lubricant is typical for this bearing family?
Oil lubrication is standard for the higher end of the speed range shown in the size table above; grease is common at the lower-speed, higher-load end of typical applications, such as crane hooks and screw presses, where speed is low enough that oil's cooling advantage matters less.
Boundary dimensions and speed ratings for the 29300 series shown here have been verified against currently listed part numbers. Dynamic and static load ratings are not yet populated in the product data for these specific SKUs at the time of writing — the figures above are drawn from independent manufacturer catalogs and should be confirmed against the current supplier spec sheet, or against internal product data once it is filled in, before publishing or quoting.
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