LOCTITE^® 638

FAQ

What is fixture time?

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.

What is cure time?

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

What is the optimum fit/clearance for anaerobic retaining compounds?

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.

What is the temperature range of anaerobic retaining compounds?

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.

Which retaining compound should I use for slip fits, press fits or bonded heat shrink fits?

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.

My application requires two parts to be bonded and sealed to prevent ingress of oil – is this possible?

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

What affects the cure speed of anaerobic adhesives and how do I overcome this?

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.

How do I disassemble components bonded with LOCTITE^® anaerobic adhesives?

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.

Are anaerobic retaining compounds resistant to gasoline, diesel, engine oil, water, glycol, acids, alkalis, hydraulic fluid, etc.?

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.

What health and safety (H&S) precautions do I need to take with product "X"?

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.

How can I tell if parts have been bonded without having to test them?

Good news, this product will fluoresce under UV light, allowing for visual inspection and confirmation that the assemblies have been bonded successfully.

Can I apply retaining compounds directly onto machined/as-received parts?

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.