LOCTITE® 660 High Strength Retaining Compound

Even in the best-press-fit application (mechanical) there is only 20% to 40% actual metal contact between the surfaces – leaving gaps between fitted parts which cause cylindrical assembly failure. LOCTITE can achieve 100% contact by filling the gap completely: by filling all the voids between the parts we increase the overall strength of the assembly by up to three times that of the original press fit. Thus, retaining compounds secure bearings, keyways and cylindrical parts into housings or onto shafts, forming strong assemblies. Making it an effective and economical method to eliminate challenges like loosening, corrosion backlash and wearing by unitizing the assembly and provide uniform stress distribution. In a nutshell: Benefit of use Adhesive Solutions vs. Alternatives: - Adhesive Solution: Retaining Compounds fill the inner space between the components and cure anaerobically to form a strong unitized assembly. Once cured, RCs provide high shear strength with maximum load transmission capability and uniform stress distribution, while also eliminating fretting corrosion They improve reliability, eliminate failures, and reduce overall costs in customer operations. - Mechanical: Conventional assembly methods include pins, key/keyway assemblies; splines; clamp rings, press fits, shrink fits, taper fits; welding and soldering. These methods often require special machining, resulting in costly and time-consuming assembly procedures, and do not uniformly distribute the load forces, which can result in premature wear and failure of the assembled components.

The optimum fit for thinner / low viscosity products like LOCTITE® 603 is 0.025 mm to 0.08 mm. For thicker / high viscosity products like LOCTITE® 638, it is 0.05 mm to 0.1 mm. Optimum clearance (D-d) is application and substrate specific. Please contact Henkel's technical team for details and guidance.

The standard continuous operating temperature range for LOCTITE® anaerobic adhesives is -55˚C to +150˚C. Depending on the specific application requirements, high-performance grades are also available offering increased temperature resistance. Please consult with the Henkel technical team for availability and grade selection.

Some LOCTITE® anaerobic adhesives will fluoresce under UV light, allowing for visual inspection and confirmation that the assemblies have been bonded successfully.

Some LOCTITE® anaerobic adhesives have been formulated to be tolerant to light oil contamination of parts, allowing for immediate application and eliminating additional cleaning processes in some applications. Contamination levels may vary. Excessive contamination and using an adhesive which is not oil tolerant will reduce the strength and overall success of a bonded assembly. Please speak to Henkel's technical team for information and guidance.

Fixture time is the time taken for the adhesive to provide initial handling strength (defined as 0.1N/mm²). Once fixtured, the assembly can usually be handled/moved on for further processing.

Cure time is the time taken for the adhesive to reach its final mechanical properties.

Product selection is specific to each application. As a rule of thumb, thinner/low viscosity products are used for tighter fitting parts with low diametrical clearance; thicker/high viscosity products are used where gap-filling capability is needed. Bonded heat shrink-fit assemblies will utilize a low viscosity product with high thermal resistance, e.g. LOCTITE® 648. For slip-fitted assemblies, apply to the leading edge of the male part and female parts. Assemble with a twisting motion. For press-fitted assemblies, apply adhesive generously to both bond surfaces and assemble with a high press on rate. For shrink fitted assemblies, apply adhesive to the shaft, and heat the collar to create sufficient clearance for free assembly.

Yes, all LOCTITE® anaerobic adhesives will lock and seal components and assemblies, preventing failure from vibrational loosening and corrosion.

There are several factors which will affect the cure speed or fixture time of Henkel anaerobic adhesives - most notably the substrate material, the bond gap and the application temperature. Anaerobic adhesives cure by the chemical reaction with active metal ions (specifically iron or copper) and the exclusion of air within small gaps to cure. If the substrates are passive (low iron or copper content), or the ambient temperature is low, the cure reaction may be slow. In these circumstances an activator can be applied to the substrate prior to bonding to speed up the reaction. Alternatively, the components can be heated to speed up the reaction and reduce the fixture and cure time. Please see more details on the relevant technical data sheet.

If the parts cannot be separated using mechanical methods alone, Henkel recommends applying localized heat to the components for several minutes before applying force. Long-term exposure to temperatures in excess of 500°F/260°C will start to degrade the adhesive and can aid disassembly.

Yes, Henkel anaerobic adhesives become highly resistant thermoset polymers once cured, making them suitable for a vast number of applications. Consult the online product resources or contact our technical teams for further information.

All necessary H&S measures and PPE (personal protection equipment) requirements can be found on the product material safety data sheet, all of which are available via our website.