Bearing retaining compounds: LOCTITE 609, 620, 638, 641, 648, 660, 668 and 680
A bearing retaining compound bonds a specified cylindrical metal interface, such as a ring to its shaft or housing. It is not lubricant inside the bearing. Choose it from the measured joint clearance, materials, temperature, required retention, cure conditions and future disassembly needs—not from colour or a claim that one adhesive is best for every bearing.
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Bearing glue, bearing fit compound and bearing retainer: identify the actual task
“Green Loctite” is not a complete specification. Several retaining products are green, and their viscosity, strength, gap guidance and serviceability differ. Record the product number and applicable regional/formulation data sheet. A stud-and-bearing compound label does not establish equivalence across manufacturers.
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| Search term / product type | Intended function | Do not confuse it with |
|---|---|---|
| Bearing retaining compound / bearing fit adhesive | Bond a specified cylindrical mating interface | Grease between balls or rollers and raceways |
| Threadlocker | Retain a threaded fastener using its own specification | A universal substitute for a cylindrical-seat retaining compound |
| RTV or gasket sealant | Seal a designated joint in a compatible application | A structural bearing-seat repair |
| Bearing retainer / cage | Mechanical separator or retaining component, depending on context | An adhesive product merely because both use the word retainer |
Which retaining compound fits the selection problem?
Manufacturer-scoped reference, not a sales ranking or an approval to repair any bearing seat. The source editions are listed below; confirm the data sheet supplied for the actual product.
LOCTITE 641 is the explicit service-disassembly option in its cited data sheet; 638 and 648 are high-strength alternatives with different viscosity and gap descriptions. Select for the actual joint, not the highest number in the product name.
The 638, 648 and 660 gap statements are the manufacturers’ bond-gap descriptions, not universal machining tolerances. The Permatex value explicitly states diametral gap. Verify each product’s definition and procedure before using a clearance value.
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| Product | Form / stated strength class | Reference use or gap statement | Selection boundary |
|---|---|---|---|
| LOCTITE 609 | Low-viscosity, high-strength liquid | Close-fitting metal cylindrical joints; press-fit augmentation | Do not choose it solely because it is green |
| LOCTITE 620 | High-viscosity, medium-to-high-strength liquid | Heat-related retaining applications; verify cure and operating conditions | Heat resistance does not waive the bearing, grease and seal limits |
| LOCTITE 638 | High-viscosity, high-strength liquid | TDS describes bond gaps approaching 0.25 mm | Gap, substrate and surface preparation still govern |
| LOCTITE 641 | Medium-strength liquid | Joints where planned disassembly is important | Serviceable does not mean every bonded bearing can be removed by hand |
| LOCTITE 648 | Low-viscosity, high-strength liquid | TDS describes bond gaps approaching 0.15 mm | Do not substitute the 638 gap reference |
| LOCTITE 660 | High-viscosity, high-strength paste | TDS describes cylindrical repair gaps approaching 0.50 mm | A repair candidate is not proof that a damaged seat is concentric or structurally sound |
| LOCTITE 668 | Waxy retaining stick | Controlled placement on cylindrical metal joints | Stick format is not ordinary grease and is not an interchangeable threadlocker |
| LOCTITE 680 | Medium-viscosity, high-strength liquid in the cited TDS | Cylindrical metal retention; named formulation tolerates minor oil contamination | Oil tolerance does not eliminate cleaning or compatibility checks |
| Permatex Bearing Mount for Close Fits | Close-fit retaining liquid, TDS 60950 | Listed diametral gap up to 0.005 in, exactly 0.127 mm | Do not infer equivalence to another product from colour or part-number similarity |
Diametral gap vs radial adhesive thickness
For ideal concentric cylinders, diametral clearance equals bore diameter minus shaft diameter. The radial space on one side is half that value. A 50.04 mm bore around a 50.00 mm shaft therefore gives 0.04 mm diametral clearance and 0.02 mm radial space. This is geometry, not approval of the fit.
If the shaft sits off-centre, the local adhesive thickness is not uniform. Out-of-roundness, taper, fretting, scoring and a spun ring can make a single measured diameter misleading. Measure the damaged seat before considering a compound.
An interference fit has a different sign and assembly mechanism from a positive-clearance slip fit. Do not create extra clearance simply to match an adhesive example without checking the bearing arrangement and the engineered fit.
Published shear values: keep the test conditions attached
Selected steel pin-and-collar compressive shear values from the named Henkel TDS, using ISO 10123. MPa equals N/mm². These are not controlled same-condition head-to-head tests and are not allowable bearing loads.
A ≥ value is a stated minimum in that data entry; a value without that sign is not silently converted into a minimum. Different cure times, temperatures, materials and test specimens prevent a simple strongest-to-weakest ranking.
The listed shear result is not the rolling bearing’s dynamic capacity C, an allowable shaft torque, or a machine safety factor. Joint design, bonded geometry and real loading would need their own validated calculation. Do not put these MPa values into the bearing life calculator as a load rating.
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| LOCTITE product | Reported MPa | Cure condition in TDS | TDS edition |
|---|---|---|---|
| 609 | ≥15.8 | 24 h at 22 °C | September 2014 |
| 620 | 17 | 24 h at 23 °C | April 2022 |
| 638 | 29 | 72 h at 23 °C | May 2024 |
| 641 | ≥6.5 | 24 h at 22 °C | May 2004 |
| 648 | 31 | 72 h at 23 °C | May 2021 |
| 660 | ≥17.2 | 24 h at 22 °C | December 2009 |
| 668 | ≥7 | 24 h at 22 °C | August 2018 |
| 680 | ≥19.3 | 24 h at 22 °C | August 2016 |
Cleaning, activator and cure time
Retaining compounds cure in a suitable confined metal joint. Cure rate changes with substrate, gap, temperature and the specified activator. A fixture or handling time is not the same as full cure or a release-to-service time for the machine.
Permatex TDS 60950 reports hardening in 4 hours and full cure in 24 hours for its stated reference. That is not a timing rule for all eight LOCTITE products, a cold workshop, a passive substrate or a large gap.
Clean and prepare the mating surfaces according to the exact data sheet. The oil-tolerance statements for named products are not permission to bond through heavy grease, dirt or an unknown cleaner residue. Check cleaner and activator compatibility; do not add arbitrary solvent to thin the adhesive.
Avoid applying the compound to polymer components without explicit compatibility approval. Several cited data sheets warn about plastics and stress cracking. Read the current safety data sheet and use the required ventilation, eye and skin protection.
Loose bearing, worn housing or spun outer race: when glue is not the answer
The 660 data sheet includes worn-fit restoration among its applications, but a particular damaged shaft or housing still needs a valid repair decision. A sleeve, machining, replacement or a specified bonded repair may be appropriate only after the geometry and duty are established. BearingScope does not declare an unidentified loose seat safe to glue.
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| Condition | Required check | Why a compound alone is insufficient |
|---|---|---|
| Ring creeps on a nominally sound seat | Fit, operating temperature, load direction and housing/shaft accuracy | Retention may be one part of an engineered solution, not proof the original fit is correct |
| Worn or spun seat | Roundness, taper, cracks, material loss and concentricity | Gap filling does not automatically recreate the bearing centreline or restore structure |
| Non-locating ring must move axially | Original thermal-expansion arrangement | Bonding the sliding interface can create unintended axial constraint |
| Wheel, hub or other safety-critical assembly | OEM repair limits and approved process | A generic bearing adhesive chart does not approve a road-vehicle repair |
| Plastic housing or unusual material | Product/substrate compatibility and joint design | Metal retaining-compound assumptions cannot simply be transferred to plastics |
Plan removal before choosing a high-strength compound
If regular service removal is a core requirement, include it in selection rather than treating the strongest available bond as automatically preferable. The cited 641 product is designed with service disassembly in mind; the complete fit and geometry still determine removal effort.
Some retaining-compound instructions use localized heat to assist dismantling. Those adhesive removal procedures are not permissible operating temperatures for the bearing, lubricant, seals, shaft or housing. Heating a whole greased or sealed assembly indiscriminately can damage it and create hazards.
Use a controlled equipment-specific removal method and suitable pulling or pressing support. Protect adjacent parts and do not transmit extraction forces through rolling contacts when the relevant ring can be supported. Do not assume the removed bearing remains reusable after an adhesive-release operation.
Common comparisons: 609 vs 641, 638 vs 648, 620 vs 680
LOCTITE 609 vs 641 for a bearing?
609 is a low-viscosity, high-strength retaining product in its cited TDS. 641 is medium strength and explicitly addresses planned service disassembly. Measure the joint and check cure and operating requirements before choosing; colour is not a selection rule.
LOCTITE 638 vs 648: are they interchangeable?
Both are high-strength retainers, but the cited 638 sheet describes higher viscosity and gaps approaching 0.25 mm, while 648 describes lower viscosity and gaps approaching 0.15 mm. Their published strength values also have defined test conditions. Do not treat a similar application label as blanket interchangeability.
LOCTITE 620 vs 680 for high temperature?
Compare the exact product’s temperature-dependent performance and cure conditions, then check the bearing, seal and lubricant limits. 620 is described as high viscosity and 680 as medium viscosity in the cited sheets. A heat-related adhesive claim alone does not approve the complete assembly.
Can retaining compound be used with a press fit?
Some cited products include press-fit applications, but compatibility with a particular fit, assembly method and load must be established. Adhesive is not a reason to force an excessive interference fit.
Is bearing retaining compound the same as grease?
No. Grease lubricates permitted rolling or sliding contacts; retaining compound bonds a selected interface. Keep it out of the bearing interior.
What is a bearing retaining stick?
LOCTITE 668 is a wax-consistency retaining product supplied as a stick in the cited TDS. It is a placement format for an anaerobic bond, not a lubricant or a universal substitute for liquid retainers.
Which product is best for a loose bearing race?
There is no sound answer without the seat measurements, damage assessment, required fit, temperature, serviceability and equipment repair limits. Establish whether the seat is repairable before choosing an adhesive.
What the evidence can — and cannot — tell you
| Observation or context | Interpretation to consider | Verification needed |
|---|---|---|
| Joint | Exact ring-to-shaft or ring-to-housing interface | Never put retaining adhesive into rolling contacts or lubricant passages. |
| Fit and condition | Measured gap, roundness, alignment and seat damage | Adhesive does not restore missing geometry by itself. |
| Service | Temperature, environment and intended axial movement | Do not bond a surface that must slide for thermal expansion. |
| Assembly | Product TDS, surface preparation, cure and removal plan | Handling strength is not permission for full load. |
Plan the work safely
Identify and record
Identify the actual joint and why retention is needed. Measure the shaft and bore at several positions and inspect the seat, ring, roundness and alignment. Reject an unsupported repair assumption before selecting adhesive.
Check the context
Use the exact product technical and safety data sheets to check clearance, materials, temperature, strength and dismantling requirements. Confirm that the machine design permits a bonded joint and preserves its locating/non-locating function.
Verify before acting
With equipment safely isolated, prepare and dry the specified mating surfaces. Protect seals, rolling contacts and lubricant paths. Apply only to the intended interface by the product procedure, assemble and remove accessible excess without contaminating the bearing.
Keep the decision traceable
Maintain the required assembly position and allow the specified cure under the actual conditions before loading. Record the compound used and its future removal requirements; verify guarded operation by the equipment commissioning procedure.
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.
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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.
- Henkel LOCTITE 609 Technical Data Sheet, September 2014 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 620 Technical Data Sheet, April 2022 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 638 Technical Data Sheet, May 2024 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 641 Technical Data Sheet, May 2004 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 648 Technical Data Sheet, May 2021 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 660 Technical Data Sheet, December 2009 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 668 Technical Data Sheet, August 2018 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Henkel LOCTITE 680 Technical Data Sheet, August 2016 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
- Permatex Bearing Mount for Close Fits, TDS 60950, September 2014 — Manufacturer-specific factual reference. Edition, test conditions, exact series and selection limits retained; not a universal equipment approval.
Source addresses and collection status are retained in the internal audit. No unpublished dimensions, torque settings, service intervals or interchange approvals are inferred.