Loctite 638 - Retaining Compound - 50ml

LOCTITE 638 is a high-strength, single-component anaerobic retaining compound designed for bonding close-fitting cylindrical metal components. It is particularly suitable for securing shafts, gears, pulleys, bushings, sleeves and other cylindrical assemblies where high strength, resistance to vibration and reliable retention are required.

LOCTITE 638 cures when confined between close-fitting metal surfaces in the absence of air. The cured adhesive fills the microscopic clearance between mating components, creating a strong bond that helps prevent loosening and leakage caused by shock, vibration and operating loads.

Key Features

High-strength retaining compound for cylindrical metal assemblies

Suitable for active and passive metals, including stainless steel and plated surfaces

High viscosity formulation helps accommodate gaps between mating components

Gap-filling capability of approximately 0.15–0.25 mm

Fixture time of approximately 4 minutes

Excellent resistance to vibration and mechanical loading

Good tolerance to minor contamination from industrial oils

High-temperature resistance up to 180°C

Green-colored liquid with UV fluorescence for inspection and quality control

Anaerobic curing technology

Typical steel shear strength of approximately 31 N/mm² (4,500 psi)

Applications

LOCTITE 638 is designed for retaining close-fitting and slip-fitted cylindrical components. Typical applications include:

Shafts and hubs

Bushings and sleeves

Gears and sprockets

Pulleys

Bearings

Rotors

Rotating assemblies

Keyways and cylindrical joints

Components requiring additional retention against vibration

Repair and maintenance of worn cylindrical assemblies

It can also be used for certain high-strength threadlocking and thread-sealing applications, although product selection should be based on the specific application and joint requirements.

How LOCTITE 638 Works

LOCTITE 638 is an anaerobic adhesive. When the adhesive is applied between closely fitting metal surfaces, exposure to air is restricted and the product begins to cure. The cured material forms a strong polymeric bond between the mating surfaces.

This allows LOCTITE 638 to provide both mechanical retention and resistance to movement, helping prevent components from slipping, rotating or loosening during service.

Performance on Metals

LOCTITE 638 can be used on a wide range of metals, including difficult-to-bond passive substrates such as stainless steel and plated surfaces. Its formulation also provides good tolerance to minor amounts of industrial oils and other surface contamination, although proper cleaning and surface preparation are recommended for maximum performance.

Temperature Resistance

LOCTITE 638 has a stated operating temperature range of approximately:

-55°C to +180°C (-65°F to +355°F)

This makes it suitable for many demanding industrial assemblies exposed to elevated temperatures.

Technical Specifications

Property

LOCTITE 638

Product type: Retaining compound

Technology: Acrylic: anaerobic

Chemical type: Urethane methacrylate

Appearance: Green liquid

Cure system: Anaerobic

Strength: High

Viscosity: Approximately 2,500 mPa·s (cP)

Fixture time: Approximately 4 minutes

Gap fill: 0.15–0.25 mm

Operating temperature: -55°C to +180°C

Steel shear strength: Approximately 31 N/mm² (4,500 psi)

Fluorescence: Positive under UV

Application: Retaining / cylindrical assemblies

Advantages for Industrial Maintenance

LOCTITE 638 can reduce the need for traditional mechanical retention methods in suitable applications. By bonding the mating surfaces, it can help improve the reliability of cylindrical assemblies and reduce movement caused by vibration and operating loads.

Its combination of high strength, high viscosity, oil tolerance and temperature resistance makes it suitable for industrial maintenance, manufacturing, automotive applications, electric motors, fluid-power equipment and remanufacturing.

Application Guidelines

For best results:

Clean and degrease the mating surfaces.

Apply LOCTITE 638 evenly to the appropriate bonding surfaces.

Assemble the components promptly.

Align the parts correctly before the adhesive cures.

Allow sufficient curing time before applying significant service loads.

For difficult or passive metals, an appropriate activator may be considered according to the Henkel technical data sheet and application requirements.

Packaging

LOCTITE 638 is available in several package sizes depending on market and application requirements. Henkel's India product page currently lists 50 ml and 250 ml bottles.

Product Summary

LOCTITE 638 is a high-strength, high-viscosity anaerobic retaining compound for securing cylindrical metal components such as shafts, gears, pulleys, bushings and sleeves. It provides reliable retention, good oil tolerance and high-temperature resistance up to 180°C, making it suitable for demanding industrial assembly, maintenance and repair applications.