In precision engineering, securing cylindrical components like bearings, bushings, gears, and shafts is mission-critical. Traditional mechanical methods—press fits, shrink fits, keys, and splines—rely solely on friction. This reliance leaves assemblies vulnerable to fretting corrosion (micro-movement), uneven stress distribution, and failure under high dynamic loads and vibration.
The definitive solution for robust mechanical assemblies is Retaining Compounds: a specialized class of anaerobic adhesive engineered to augment or replace mechanical interference fits entirely. By creating a solid, structural bond between mating metal surfaces, retaining compounds deliver unparalleled strength, reliability, and cost savings.
How Retaining Compounds Transform Cylindrical Joints
Retaining compounds are single-component, solvent-free adhesives that belong to the anaerobic family. Their unique curing mechanism ensures the bond forms only when the parts are correctly assembled.
The Anaerobic Curing Principle
- Application: The liquid compound is applied to the shaft or inner diameter of the housing.
- Confinement: When the two metal parts are assembled (e.g., a bearing pressed into a housing), the liquid is confined in the joint.
- Cure Trigger: The absence of air (oxygen) and the catalytic presence of metal ions (from the iron, steel, or copper surfaces) trigger a rapid polymerization.
This reaction transforms the liquid into a tough, durable thermoset plastic that completely fills all microscopic gaps and surface irregularities. This action increases the contact area from a typical 20−40% for a press fit to a full 100% surface-to-surface bond.
Key Advantages Over Traditional Methods
| Feature | Retaining Compounds | Press/Shrink Fits & Keys |
| Load Distribution | 100% Uniform across the entire joint. | Localized stress points; limited to 20−40%contact. |
| Fretting Corrosion | Eliminated; no micro-movement is possible. | Common failure mode under vibration. |
| Assembly Stress | Allows looser (slip) fits; zero installation stress. | Requires tight tolerances; introduces high internal stress. |
| Disassembly | Possible with appropriate heat/force (depends on strength grade). | Difficult; requires specialized pullers or heating/cooling. |
| Machining Costs | Reduced; allows for wider tolerances (slip fits). | High; requires expensive, precise tolerances. |
Essential Applications for Retaining Compounds
Retaining compounds are indispensable in any assembly where rotational accuracy, vibration resistance, and high shear strength are critical.
- Bearing Retention: Securing bearings onto shafts or inside housings, particularly in high-speed electric motors and gearboxes.
- Mounting Power Transmission Components: Fixing gears, pulleys, sprockets, and rotors onto drive shafts, eliminating the need for keys and splines which cause stress concentrations.
- Restoring Worn Parts: Using high-viscosity, gap-filling grades to repair worn bearing seats or keyways, salvaging expensive components from being scrapped.
- Securing Bushings and Sleeves: Locking bushings into heavy equipment pivot points or hydraulic cylinders to prevent rotation and movement.
Navigating Selection: Key Criteria for Retaining Compounds
Choosing the ideal retaining compound is not a one-size-fits-all process. Selection is driven by three critical engineering factors:
1. Strength (Permanent vs. Serviceable)
- High Strength (Permanent Bond): Used for assemblies designed to last the life of the machine, such as rotor-to-shaft bonds or large structural gears. Requires heat (often >250∘C) or significant force for removal.
- Medium Strength (Serviceable Bond): Used for parts requiring periodic maintenance (e.g., small bearings in a gearbox). Provides sufficient holding power but can be disassembled with standard hand tools or minimal localized heat (often <150∘C).
2. Gap Filling / Viscosity
The adhesive’s viscosity must be matched to the clearance between the mating parts.
| Gap Size | Viscosity Requirement | Incure Product Type (Example) |
| Tight Fit (≤0.15 mm) | Low Viscosity (Wicking Grade) | WeldLock™ 309 (High Strength Penetrant) |
| Slip Fit (0.15 mm to 0.25 mm) | Medium/High Viscosity | WeldLock™ 330 or 347 (Standard Assembly) |
| Worn Parts (>0.25 mm) | Very High Viscosity/Repair Paste | WeldLock™ 356 (Metallic Grey Repair Compound) |
3. Temperature Resistance
Most retaining compounds handle up to 150∘C. For assemblies exposed to continuous high heat (e.g., in engine compartments or high-speed spindles), a high-temperature formulation is required, often capable of withstanding up to 175∘C or more.
Partnering with Incure: Precision WeldLock™ Solutions
Incure’s WeldLock™ Retaining Compound Series is engineered to meet these precise industrial requirements. We provide the expertise to match the ideal chemistry to your assembly’s lifespan, load, and service profile.
How Incure Guides Your Selection:
- High-Speed, High-Temp Assembly: For press-fit cylindrical assemblies exposed to elevated temperatures and dynamic loads, we recommend products like Incure WeldLock™ 347 (High Strength, Fast Curing), balancing rapid assembly time with high thermal stability.
- Repair and Salvage: To restore the precision fit of worn housings or shafts without costly remachining, we select the high-viscosity, gap-filling Incure WeldLock™ 356 (Metallic Grey Repair Compound), designed to fill larger clearances (up to 0.5 mm) and eliminate the need for replacement parts.
- Serviceable Components: When disassembly is mandatory, our choice is Incure WeldLock™ 338 (Medium Strength, Yellow). This compound provides reliable retention under load but breaks down more easily for hassle-free maintenance.
By consulting Incure, you move beyond guesswork, ensuring your selection optimizes not just the initial strength, but the total lifecycle cost and maintenance requirements of your machine.
Do you have a cylindrical assembly that is failing due to vibration or fretting corrosion? Contact Incure today for a technical consultation to select the optimal WeldLock™ Retaining Compound for your application.