Retaining compounds are a fundamental tool in the world of mechanical assembly, providing a reliable and durable method for securing cylindrical metal components. Often distinguished by their vibrant green color, these anaerobic adhesives are specifically engineered to cure in the absence of air and in the presence of metal ions, forming a tough, solid plastic bond that prevents loosening due to vibration, shock, and thermal cycling.

For manufacturers and professionals, selecting the correct retaining compound is a critical decision that impacts the long-term integrity and performance of an assembly. At Incure, our WeldLock™ series of green retaining compounds offers a range of specialized solutions, each designed to meet the unique demands of different applications. Let’s explore how to choose the best option for your project.

What is a Retaining Compound and Why Use a “Green” One?

A retaining compound is a single-component liquid adhesive used to bond non-threaded, cylindrical metal parts. When applied to the clearance between a shaft and a bearing, for example, it fills the microscopic gaps, creating a 100% surface-to-surface fit. This eliminates micromovements that can lead to fretting corrosion and eventual part failure.

The “green” designation is an industry standard used to signify a specific type of high-strength, anaerobic retaining compound, particularly those with low to medium viscosity and excellent gap-filling capabilities. This color-coding simplifies product selection on the manufacturing floor.

Matching the Retaining Compound to Your Application

The key to a successful bond is understanding the specific requirements of your assembly. Here’s a breakdown of how the different WeldLock™ green retaining compounds from Incure can address various challenges:

1. For Tight, Press-Fit Assemblies: WeldLock™ 309

When you have rigid, closely-machined parts with minimal clearance, a low-viscosity retaining compound is essential. WeldLock™ 309 is designed with a low viscosity of 125 MPa·s, allowing it to easily penetrate and fill the tightest gaps up to 0.3mm. Its high shear strength of 16 N/mm² provides a reliable, long-term bond for components like gears on shafts or bushings in housings.

• Best for: Press-fit applications where parts have a small diametral clearance.
• Key Benefit: Easy penetration into tight-fitting parts.
• Practical Example: Securing a bearing into a perfectly machined bore.

2. For High Dynamic Loads and Slip-Fit Assemblies: WeldLock™ 330

For applications involving significant vibration, impact, or cyclic loading, you need a compound with higher strength and a faster cure time. WeldLock™ 330 offers a robust shear strength of 25 N/mm² and a fast fixture time of just 5 minutes. Its higher viscosity (2500 MPa·s) makes it suitable for slip-fit applications with diametral gaps up to 0.26mm, where a thicker adhesive is needed to fill the void and secure the part against movement.

• Best for: Motors, gearboxes, and heavy-duty assemblies exposed to extreme stress.
• Key Benefit: Exceptional strength under high dynamic loads.
• Practical Example: Bonding a rotor to a motor shaft in an electric motor.

3. For High-Temperature and Press-Fit Environments: WeldLock™ 347

In assemblies that experience elevated operating temperatures, a standard retaining compound may not suffice. WeldLock™ 347 is specifically engineered to perform under heat, with a temperature resistance up to 175°C. It combines this thermal stability with a high shear strength and a fast 5-minute fixture time, making it ideal for press-fit applications in demanding environments.

• Best for: Components in gearboxes, motors, and mechanical drives that generate heat.
• Key Benefit: High-performance bonding in high-temperature conditions.
• Practical Example: Securing a gear on a shaft in a high-speed industrial gearbox.

4. For Repair and Refitting Worn Parts: WeldLock™ 365

When dealing with worn components or assemblies with larger tolerances, a retaining compound with excellent gap-filling capabilities is required. WeldLock™ 365 is the go-to solution for refitting worn shafts or housings. It can fill gaps up to 0.25mm and provides a high-strength bond that restores the integrity of the assembly, saving the cost of replacing parts. Its viscosity of 1250 MPa·s strikes a balance, flowing easily into worn spaces while providing the body needed for a strong bond.

• Best for: Repair and maintenance, as well as slip-fit assemblies with wider gaps.
• Key Benefit: Restoring worn parts and improving fit.
• Practical Example: Repairing a worn keyway on a shaft or securing a bearing in a slightly oversized housing.

Actionable Advice for Your Assembly Process

1. Cleanliness is Crucial: Always ensure metal surfaces are clean, dry, and free of oil, grease, or other contaminants. This is the single most important factor for a strong, reliable bond.
2. Verify the Gap: Measure the diametral clearance between your components. Choose a retaining compound with a gap-filling capability that matches or exceeds your measurement.
3. Cure Properly: Anaerobic compounds require a tight metal-to-metal fit to cure effectively. If an assembly has a large gap, consider a different product or an activator to aid the curing process.

At Incure, we are committed to providing manufacturers and professionals with the right tools for the job. Our WeldLock™ series is a testament to this, offering a specialized range of high-quality retaining compounds that deliver precision, strength, and durability for a wide variety of industrial applications.