A spherical plain bearing lets a loaded joint tilt and oscillate without using balls or rollers. Selecting the ring size is only the beginning. The sliding pair, load direction, fit, housing support, lubrication and sealing decide whether it works in the machine.
A spherical plain bearing is a sliding bearing with a convex spherical surface on the inner ring and a matching concave surface in the outer ring. This geometry carries load while allowing oscillation, tilting and angular misalignment between the shaft and housing. There are no balls or rollers between the two sliding surfaces. Radial designs mainly support radial load; angular contact and thrust designs address different load directions.
Many purchase requests begin with a bore and a familiar GE designation. That identifies the envelope, but it does not tell us how the bearing is loaded or installed. Two bearings that fit the same shaft can have different sliding materials, maintenance plans, sealing and allowable motion.
Our factory review starts with the joint, not the part number. We look at where the force enters the inner ring, how the outer ring is supported, how far the axes move, and whether grease or contamination can reach the sliding surfaces. The catalog number comes after those questions.
1. How a spherical plain bearing moves under load
The spherical interface is the defining feature. The inner ring has a cylindrical bore for the shaft or pin and a convex outside surface. The outer ring has a cylindrical outside diameter for the housing and a concave raceway around the inner ring. As the inner ring tilts, the center of the spherical surfaces remains common.
This is sliding contact. A conventional ball bearing separates its rings with rolling elements. A spherical plain bearing lets its paired surfaces slide directly or across a liner. That difference makes it suitable for high load and limited oscillating movement, but it also makes sliding speed, pressure, wear and lubrication central to selection.
The bearing can accommodate angular misalignment. It should not be treated as permission for uncontrolled shaft deflection or poor housing alignment. If a joint needs an integral threaded connection instead of a separate housing, compare this design with a rod end bearing.
2. Radial, angular contact and thrust are load-direction choices
The word "spherical" describes the sliding geometry. It does not mean every bearing carries every load direction equally. The first useful division is where the main load acts relative to the bearing axis.
Radial spherical plain bearing
Main load acts across the bearing axis. It may accept a simultaneous axial component according to the exact design and manufacturer's calculation method.
Angular contact type
Geometry is arranged for combined radial and axial load. Direction and bearing arrangement matter, especially if axial load can reverse.
Thrust spherical plain bearing
Main load acts along the bearing axis. A radial guide may be required separately when the assembly also has radial force.
Schaeffler's official engineering reference separates these types in the same way: radial bearings support radial and combined loads, angular contact bearings support axial forces with radial forces, and axial designs are intended for axial support. Dongzhou's current category is specifically radial spherical plain bearings.
ISO 12240-1:1998 covers dimension series, tolerances and radial internal clearances for radial spherical plain bearings. ISO states that the standard allows a wide choice of sliding material combinations. It standardizes key geometry and clearance, not one universal material or manufacturer load value.
3. The sliding pair changes maintenance and behavior
Bore size gets the attention because it is easy to measure. The sliding pair usually tells us more about how the bearing should be used.
| Sliding contact | Typical service approach | Useful characteristics | Questions before selection |
|---|---|---|---|
| Steel-to-steel | Maintenance-required | Suitable for demanding load, shock and alternating duty when the lubrication plan works | Can grease reach the loaded zone? What is the relubrication method and contamination level? |
| Steel-to-bronze | Usually maintenance-required | Uses a dissimilar-metal sliding pair and may suit applications needing a serviceable bearing | Which lubricant, pressure, speed and temperature apply to the exact series? |
| Steel-to-PTFE composite | Maintenance-free | Low friction and no routine relubrication when the liner and environment match the duty | Is the load constant or reversing? Can dirt, solvent, edge load or installation damage reach the liner? |
These are selection directions, not cross-brand ratings. Material recipes, load calculations and operating limits remain manufacturer-specific.
Maintenance-free still requires inspection. It means the sliding system does not need routine relubrication during its intended service, not that the bearing can be ignored. A damaged liner, loose housing fit or contaminated seal remains a mechanical problem.
For a steel-to-steel bearing, a grease hole is useful only when the machine supplies suitable grease at a suitable interval. Schaeffler notes that lubricant selection depends on load, direction, swivel angle, sliding velocity, temperature and environment. A generic calendar interval cannot replace those application inputs.
4. What the current Dongzhou range actually shows
The table below comes from Dongzhou's live product pages. We have kept the descriptions at series level because the site does not label the load-rating unit in its product tables. That unresolved unit should be confirmed from the current catalogue before load values are published in an article or copied into an RFQ.
| Dongzhou family | Current page-listed construction | Service | Size system shown | Drawing point to confirm |
|---|---|---|---|---|
| GE UK | Two-piece, steel-to-PTFE composite; pressed outer ring; chromium-plated inner spherical surface | Maintenance-free | Metric; GE 6 UK through GE 30 UK currently listed | Bore, outside diameter, widths, angle, fit and actual load case |
| G PW | PTFE-lined family with brass H62, carbon steel or stainless outer-ring options and GCr15 or 440C inner-ring options by designation | Maintenance-free | Metric; G 5 PW through G 50 PW currently listed | Exact material suffix, corrosion exposure and required clearance |
| COM / HCOM | Steel-to-steel; carbon-steel outer ring; GCr15 inner ring with hard chromium plating; lubrication groove and holes | Maintenance-required | Inch dimensions | Lubrication route, shock or reversing duty, shaft and housing fit |
| COM..T / HCOM...T | Steel-to-PTFE composite; carbon-steel outer ring; GCr15 inner ring with hard chromium plating | Maintenance-free | Inch dimensions shown in the product table | Space, load direction, liner duty and mating component tolerances |
| GE E / GE ES / GE ES-2RS | Steel-to-steel, phosphated rings and an axially split outer ring; ES has lubrication grooves and holes; 2RS adds seals on both sides | Maintenance-required | Metric; GE 4 E through GE 200 ES currently listed | Open or sealed form, grease access, split orientation and housing support |
Source: Dongzhou live product pages checked September 10, 2026. Product availability and final specifications should be reconfirmed at quotation.
5. Load is dynamic whenever loaded surfaces slide
A stationary bearing under a changing force can still be a static load case if there is no relative sliding at the loaded surfaces. Once the rings oscillate or tilt under load, wear enters the calculation. SKF's official load guidance classifies that condition as dynamic load and treats alternating high-frequency load or vibration as a special dynamic case where fatigue may also matter.
This distinction is more useful than asking only for a "maximum load." For selection, document:
- Direction: radial, axial or combined, plus whether the direction stays constant or reverses.
- Movement: oscillation angle, tilt angle, rotational component, frequency and duty cycle.
- Magnitude: normal load, peak load, shock and any load present while the bearing is stationary.
- Required result: service life, allowable clearance, running torque and inspection or replacement criteria.
A radial bearing may accept a simultaneous axial component, but the combined load requires the exact manufacturer's factor or calculation. Do not convert a general statement about axial capability into a universal percentage.
6. The shaft, housing and mounting process are part of the bearing
A correct bearing in an unsuitable seat can lose clearance, creep in the housing or crack. The fit determines how the inner ring expands and how the outer ring contracts after installation. Heavy or shock loading may need more interference, while too much interference can remove the operating clearance.
SKF's radial-location guidance ties shaft and housing fits to load, sliding material and adjacent-component strength. It also warns that housing deformation can distort a bearing and that fit-induced ring deformation changes internal clearance. This is why a tolerance copied from another bearing type is weak evidence.
Installation force must follow the ring being fitted
Do not press the outer ring into a housing by pushing through the inner ring and sliding interface. The mounting force should act on the ring with the interference fit. The shaft, housing and tools should be clean, dimensionally correct and free of burrs.
For a fractured or split outer ring, orientation matters. SKF's mounting instructions place the joint at 90 degrees to the load direction and warn against hammer or pin-punch installation. Those details belong on the assembly drawing or work instruction, not in an operator's memory.
Seals and grease paths need space
A 2RS suffix identifies seals on both sides for the applicable series. Seals reduce contamination entry, but they do not make the bearing immune to dirty washdown or incompatible chemicals. For maintenance-required designs, the housing should deliver lubricant to the bearing groove or hole without blocking the path during assembly.
7. Four selection mistakes we would correct before quoting
- Choosing by bore alone. The same bore does not guarantee the same outside diameter, width, tilt angle, clearance, material or load method.
- Treating self-alignment as unlimited motion. The ring can tilt within its geometry. Contact at the race edge is a different condition and can shorten life.
- Calling every load "static" because speed is low. Slow oscillation under load still creates sliding and wear, so it belongs in a dynamic review.
- Ignoring the installed state. Fit, housing wall thickness, split orientation, shoulders, grease access and contamination control can govern the result.
One more issue appears in replacement projects: a familiar suffix can look universal. It is safer to send the old drawing and the operating condition. We can then compare geometry and construction without claiming cross-brand interchangeability from the name alone.
8. What to include in a useful spherical plain bearing RFQ
A photo identifies the general bearing family. A section drawing tells us how it must work. Mark the following inputs rather than sending only "GE bearing, heavy duty."
-
Envelope
Bore d, outside diameter D, inner-ring width B, outer-ring width C and available shoulder space. -
Load
Radial and axial components, normal and peak values, shock, reversal and the units used. -
Motion
Oscillation, tilt or rotation; angle per cycle; frequency, duty cycle and dwell time. -
Fits
Shaft and housing materials, tolerance classes, wall thickness, retention and mounting method. -
Environment
Temperature, dust, water, chemicals, cleaning process and corrosion exposure. -
Service target
Lubrication access, inspection interval, allowable clearance, life target and failure consequence.
If the available bearing envelope is fixed but the sliding pair or surrounding geometry is not, include that distinction. Dongzhou states that it develops non-standard mechanical parts from customer drawings or samples. A sample helps us measure the existing shape; the load and operating information still have to come from the machine owner.
Drawing review by Dongzhou
Send the bearing seat with the bearing code
Mark the shaft, housing bore, shoulders, load direction, extreme joint angles and lubrication path on one section drawing. Dongzhou can compare the requirement with GE UK, G PW, COM/HCOM, COM..T/HCOM...T or GE ES-2RS families, then review non-standard geometry when a catalog envelope does not fit.
Frequently asked questions
What does a spherical plain bearing do?
A spherical plain bearing transmits load between a shaft and housing while allowing oscillation, tilting and angular misalignment. Its convex inner-ring surface slides against a matching concave outer-ring surface. Unlike a ball bearing, it has no rolling elements between those surfaces.
What is the difference between a spherical plain bearing and a rod end?
A spherical plain bearing is the inner and outer ring bearing unit installed in a separate housing. A rod end combines a spherical plain bearing with an eye-shaped housing and an integral male or female threaded shank. The sliding principle is related, but the connection and load path are different.
Can a radial spherical plain bearing carry axial load?
A radial spherical plain bearing may carry some axial load together with radial load, but the allowable combination depends on the exact bearing and sliding contact surface. Calculate an equivalent load using the manufacturer's method. Use an angular contact or thrust spherical plain bearing when the load direction requires it.
What is the difference between maintenance-free and maintenance-required spherical plain bearings?
Maintenance-free designs use a self-lubricating sliding layer such as PTFE composite and do not require routine relubrication. Maintenance-required designs commonly use steel-to-steel or steel-to-bronze contact and need a defined lubricant and relubrication plan. Both types still need inspection and protection from unsuitable contamination or mounting damage.
What does 2RS mean on a spherical plain bearing?
The suffix 2RS identifies seals on both sides for the applicable bearing series. Seals help protect the sliding surfaces from contamination, but their material and temperature limits remain series-specific. Confirm the exact manufacturer drawing because suffix details are not universal across every product family.
What information should a spherical plain bearing RFQ include?
Include the bore, outside diameter, ring widths, housing and shaft fits, radial and axial load components, load direction, oscillation or tilt angle, speed or frequency, duty cycle, temperature, contamination, sealing, lubrication access, clearance requirement and expected service life. A section drawing is more useful than a model name alone.
