Slewing ring bearings: types, dimensions, gears & selection
A slewing ring supports a rotating structure while transferring axial force, radial force and an overturning moment to its mounting structure. Start with the complete load case, mounting arrangement and drive, not just outside diameter. Four-point ball, crossed-roller, three-row roller and sliding-element rings are different design choices, not automatic substitutes.
On this page19 sections ⌄
What a slew ring carries: three loads, one load path
The bearing rings, fasteners and companion structure form a connected load path. A catalogue bearing rating cannot establish the capacity of an unsupported flange, unverified bolt joint or complete machine.
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| Quantity | Meaning | Selection implication |
|---|---|---|
| Axial force | Force parallel to the rotation axis | Include the supported mass and additional service forces. |
| Radial force | Force perpendicular to the rotation axis | Account for side loads; do not assume an axial rating covers them. |
| Overturning moment | Load tending to tilt one ring relative to the other | An offset load can dominate even when its weight seems modest. |
| Drive torque | Torque turning the structure about its rotation axis | A separate requirement from overturning-moment capacity. |
Four-point ball vs crossed roller vs three-row roller
More rollers or more rows is not a universal ranking. Compare the actual load combinations, stiffness, friction, speed and space requirements. A precision rotary table also needs quantified runout, clearance/preload and structural stiffness.
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| Construction | How to distinguish it | Documented example / boundary |
|---|---|---|
| Four-point contact ball | Ball/raceway geometry supports combined loads in a compact ring arrangement. | Kaydon RK and HS. HS uses a rectangular section; RK uses a flanged section. |
| Crossed roller | Neighbouring cylindrical rollers have alternating axes in the raceways. | Kaydon XR targets stiffness and low turning resistance; its capacities are not inferred from a ball-ring rating. |
| Three-row roller | Separate roller rows take radial and opposing axial loads; axial rows also react moment. | Kaydon TR requires particularly stiff, flat supporting structures. |
| Sliding-element ring | Polymer bearing elements slide instead of a ball or roller raceway. | igus PRT is a different tribological system; do not apply rolling-bearing grease or life rules automatically. |
Internal gear, external gear and a complete slew drive
Rothe Erde describes its slew-drive modules as a housed ball bearing and worm screw; its published design is not self-locking and needs an additional brake. Verify the particular drive, output torque and holding/braking specification. The tooth module or diametral pitch, pressure angle, tooth count and backlash are separate identification fields.
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| Arrangement | Identify | Do not infer |
|---|---|---|
| No gear | A ring without integral drive teeth | The complete machine has no drive or needs no retention. |
| Internal gear | Teeth face the centre opening | The same bore or pinion as a non-geared ring. |
| External gear | Teeth are on the outside perimeter | Interchangeability from outside diameter alone. |
| Slew drive module | A bearing and transmission packaged together | That every worm drive is self-locking or includes a brake. |
Real model examples: Kaydon RK and HS dimensions
Selected public manufacturer rows, reviewed 2 October 2026. Inch values are the original catalogue dimensions; millimetres are calculated using exactly 25.4 mm/in and displayed to three decimals. OD and ID are not the raceway pitch diameter or bolt-circle diameter.
These records are dimension references, not a ranking or replacement list. A higher published moment number does not validate the same installation or combined-load case. The source's moment rating is kept separate from the dynamic L10 capacities used in other bearing series.
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| Kaydon model | Gearing | OD in / mm | ID in / mm | Approx. mass lb | Moment rating ft·lbf |
|---|---|---|---|---|---|
| RK6-16P1Z | None | 20.390 / 517.906 | 11.970 / 304.038 | 58 | 22,700 |
| RK6-16N1Z | Internal | 20.390 / 517.906 | 12.850 / 326.390 | 65 | 22,700 |
| RK6-16E1Z | External | 19.900 / 505.460 | 11.970 / 304.038 | 72 | 22,700 |
| RK6-43P1Z | None | 47.170 / 1198.118 | 38.750 / 984.250 | 153 | 75,500 |
| RK6-43N1Z | Internal | 47.170 / 1198.118 | 39.133 / 993.978 | 188 | 75,500 |
| RK6-43E1Z | External | 46.867 / 1190.422 | 38.750 / 984.250 | 189 | 75,500 |
| HS6-16P1Z | None | 20.400 / 518.160 | 12.000 / 304.800 | 103 | 50,500 |
| HS6-16N1Z | Internal | 20.400 / 518.160 | 12.850 / 326.390 | 92 | 50,500 |
| HS6-16E1Z | External | 19.900 / 505.460 | 12.000 / 304.800 | 85 | 50,500 |
| HS6-43P1Z | None | 47.180 / 1198.372 | 38.750 / 984.250 | 269 | 139,900 |
| HS6-43N1Z | Internal | 47.180 / 1198.372 | 39.130 / 993.902 | 253 | 139,900 |
| HS6-43E1Z | External | 46.870 / 1190.498 | 38.750 / 984.250 | 237 | 139,900 |
The mounting pattern can differ when the envelope looks similar
The same selected model set is shown below. Bolt-circle diameters remain in source inches. Hole counts do not specify fastener strength, thread engagement or tightening torque.
Check the detailed drawing for threaded versus clearance holes, hole size, counterbores, orientation and tolerances. Two rings that share OD and ID can still have incompatible mounting patterns and section stiffness.
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| Model | Outer bolt circle in | Outer hole count | Inner bolt circle in | Inner hole count |
|---|---|---|---|---|
| RK6-16P1Z | 19.250 | 8 | 13.130 | 12 |
| RK6-16N1Z | 19.250 | 8 | 14.880 | 12 |
| RK6-16E1Z | 18.000 | 8 | 13.130 | 12 |
| RK6-43P1Z | 46.000 | 18 | 39.880 | 24 |
| RK6-43N1Z | 46.000 | 18 | 41.500 | 24 |
| RK6-43E1Z | 44.630 | 20 | 39.880 | 24 |
| HS6-16P1Z | 19.000 | 8 | 13.500 | 12 |
| HS6-16N1Z | 19.000 | 8 | 14.880 | 16 |
| HS6-16E1Z | 18.000 | 14 | 13.500 | 12 |
| HS6-43P1Z | 45.620 | 20 | 40.250 | 24 |
| HS6-43N1Z | 45.620 | 20 | 41.500 | 36 |
| HS6-43E1Z | 44.630 | 32 | 40.250 | 24 |
Large, small and heavy-duty are not complete specifications
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| Record before comparing | Required detail |
|---|---|
| Envelope | OD, ID, height, available space and centring features. |
| Duty | Speed, oscillation angle, cycles, reversals and required service life. |
| Load cases | Axial/radial force and overturning moment together, including start/stop and exceptional loads. |
| Accuracy | Runout, clearance or preload, positioning requirements and structural deflection. |
| Environment | Temperature, contamination, corrosion, seal and lubricant compatibility. |
| Drive and installation | Gear/pinion details, bolt joint, support flatness/stiffness and access for maintenance. |
Application examples are starting points, not machine fitment
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| Application | Documented bearing-family context | What is still needed |
|---|---|---|
| Industrial rotary tables, displays and packaging | Kaydon RK application examples | Table eccentricity, duty, accuracy and mounting. |
| Cranes, lifts and rotators | Kaydon HS application examples | The exact crane load cases, drawing and certification requirements. |
| Stiff rotary joints and machine tools | Kaydon XR crossed-roller examples | Runout/preload, drive torque and structural stiffness. |
| Stackers, reclaimers and mining shovels | Kaydon TR three-row roller examples | Machine-specific load envelope and supporting structure. |
| Excavator swing support | Rothe Erde identifies excavators as a slewing-bearing application | Machine model, serial range, complete gear and bolt pattern; no generic replacement approval. |
| Lightweight sliding rotary arrangements | igus PRT family | The particular pad material, allowable load/speed combination and environment. |
Manufacturer and product-family reference
This is a documented set of examples, not an exhaustive manufacturer catalogue. Named queries for other manufacturers remain separate research tasks; similar dimensions alone do not establish a cross-brand match.
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| Name in a search | Supported reference here | Scope |
|---|---|---|
| Kaydon / SKF Group | RK, HS, XR and TR slewing-bearing families | The source identifies Kaydon as an SKF Group company; group ownership does not rename every product as an SKF interchange. |
| thyssenkrupp Rothe Erde | Slewing rings, inspection guidance and housed slew drives | Use the actual bearing drawing/model number. |
| igus | PRT sliding-element slewing rings | A plain-bearing alternative, not a ball-bearing suffix or shared part number. |
Installation: support surfaces and the bolt joint matter
Rothe Erde requires clean, even mounting contact surfaces and full ring support. Match the drawing orientation, centring features and holes before tightening. Record flatness checks and the specified fastener condition and tightening procedure.
Do not copy torque values from a same-diameter bolt: strength class, friction, lubrication, thread engagement and installation method affect the joint. This is a preparation checklist, not permission to support or move an unsecured crane, excavator or other heavy upper structure.
Lubricate the raceway and the gearing as separate systems
Rothe Erde's raceway guidance describes lithium-soap mineral-oil NLGI 2 EP greases for its stated standard scope and treats gearing separately. This does not select grease for all manufacturers or low-temperature duties. Its intervals depend on conditions; a single calendar rule is not applied to every machine. igus describes PRT sliding elements as requiring no external lubrication, so adding industrial ring grease is not a default upgrade.
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| System | Check |
|---|---|
| Rolling raceway | The approved grease, compatibility, quantity, access and distribution around the running system. |
| Open gearing | Tooth-flank lubrication and the specified gear lubricant; do not assume preservation coating is operating lubrication. |
| Sliding-element ring | Whether the exact product is designed to run without added lubricant. |
| Duty and inspection | Operating environment, motion, downtime and evidence of lubricant condition. |
Wear measurement: compare with a commissioning baseline
Rothe Erde describes tilting-clearance and subsidence measurements. The useful quantity is change from a reference under repeatable conditions, not an isolated dial-gauge reading.
Use the approved machine procedure and bearing-specific acceptance limits; do not rock or load an unsecured assembly to obtain a reading. A drawing-specific wear limit cannot be derived from outside diameter alone. Where the permitted limit is reached or exceeded, follow the manufacturer's stop-and-inspect requirement rather than extending service from a generic table.
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| Record | Why keep it |
|---|---|
| Bearing identity and drawing | Limits depend on the bearing and application. |
| Marked measurement locations | Repeat the same positions around the ring. |
| Load direction, magnitude and machine position | A different load state can change the reading without the same amount of wear. |
| Gauge position and mounting | Structural flex and joint movement can contaminate the result. |
| Initial and current readings, dates and hours | Trend the change and inspection interval. |
| Fastener, seal and lubricant findings | Interpret clearance alongside the surrounding system. |
Drawings, CAD and catalogue limits
The example tables do not contain every dimension or tolerance needed to manufacture, install or approve a replacement. Kaydon identifies access-controlled CAD on its product pages; no protected file has been downloaded or reconstructed here. Use the exact model and revision when comparing technical documents.
A 3D-printed demonstration ring, furniture turntable or scaled drawing does not inherit an industrial slewing ring's load rating. Material, manufacture, geometry, mounting and validation remain part of the specification.
What the evidence can — and cannot — tell you
| Observation or context | Interpretation to consider | Verification needed |
|---|---|---|
| A diameter or model number | A useful identification clue | Match the complete drawing, mounting pattern and load envelope. |
| A moment rating | Resistance to an overturning load under stated conditions | Do not treat it as motor torque or an unrestricted safe working load. |
| A geared ring | A bearing with a drive interface | Check the pinion, backlash, tooth loading and braking separately. |
A practical investigation sequence
Identify and record
Record the machine, bearing drawing and revision, axial/radial loads, overturning moments and exceptional load cases.
Check the context
Compare bearing geometry, bolt circles, ring support, gear details, speed and stiffness with a documented candidate.
Verify before acting
Check the manufacturer's combined-load and mounting requirements; verify lubrication, seals, wear limits and inspection access.
Keep the decision traceable
Keep the approved drawing, installation record and commissioning reference measurements together. Do not infer a crane or excavator replacement from this example table.
Capture the information a model search cannot guess
Keep this checklist with your inspection or comparison. Checking a box only records that you have collected the item; it does not certify the bearing.
0 of 4 information groups recorded.
Technical basis & editorial scope
Original BearingScope workflow, written for catalogue research and comparison. Manufacturer material is used to check principles, not copied as a product endorsement or substituted for model-specific instructions. Reviewed 1 October 2026.
- Kaydon — RK series — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Kaydon — HS series — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Kaydon — XR crossed rollers — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Kaydon — TR three-row rollers — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Rothe Erde — Slewing bearings — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Rothe Erde — Slew drives — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Rothe Erde — Installation and lubrication — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- Rothe Erde — Wear measurement — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
- igus — PRT sliding rotary rings — Named product/family evidence only; no universal load, lubricant or fitment approval. Reviewed 2 October 2026.
Source addresses and collection status are retained in the internal audit. No unpublished dimensions, torque settings, service intervals or interchange approvals are inferred.