Loctite 641 - Retaining Compound - 50ml

LOCTITE® 641 is a one-component, medium-strength anaerobic retaining compound designed for bonding close-fitting cylindrical metal parts where regular dismantling and servicing may be required. It is particularly suitable for retaining bearings on shafts and in housings, as well as bushes, sleeves and other cylindrical fitting components. 

The adhesive cures when confined between close-fitting metal surfaces in the absence of air. Once cured, it helps prevent loosening, movement and leakage caused by shock and vibration, while its medium-strength formulation allows the assembly to be dismantled when maintenance or replacement is required. 

Key Features and Benefits

Medium-strength retaining compound

Yellow liquid

One-component formulation — no mixing required

Anaerobic curing technology

Designed for cylindrical fitting parts

Ideal for components requiring regular servicing

Helps prevent loosening caused by vibration and shock

Helps prevent leakage through the joint

Gap filling capability up to 0.15 mm

Fixture time of approximately 20 minutes

Operating temperature range of -55°C to +150°C

Suitable for steel cylindrical assemblies

Can be used with an activator when faster or more reliable curing is required on less-active surfaces. 

Typical Applications

LOCTITE 641 is suitable for:

Bearing retention on shafts

Bearings installed into housings

Bushes and sleeves

Cylindrical shafts and hubs

Rotating equipment

Electric motor components

Pumps and machinery

Industrial maintenance and repair

Close-fitting cylindrical metal assemblies

Components that need to be periodically removed for maintenance

Henkel specifically identifies bearing retention on shafts and in housings as an example application. 

How LOCTITE 641 Works

LOCTITE 641 is applied to the mating cylindrical surfaces before assembly. When the adhesive is confined between the metal surfaces and oxygen is excluded, it begins to cure.

The cured adhesive fills the microscopic clearance between the components, helping create a secure connection and reducing relative movement between the parts. This makes it useful where a conventional mechanical fit may be susceptible to vibration, shock or leakage.

Unlike a high-strength retaining compound intended for more permanent assemblies, LOCTITE 641 is formulated with medium strength to facilitate disassembly and servicing. 

Technical Specifications

Property: LOCTITE 641

Product type: Retaining compound

Strength: Medium

Technology: Acrylic / anaerobic cure

Chemical type: Methacrylate ester

Colour: Yellow

Components: One component

Cure: Anaerobic

Fixture time: Approx. 20 minutes

Gap fill: Up to 0.15 mm

Viscosity: Approx. 600 mPa·s (cP)

Operating temperature: -55°C to +150°C

Shear strength on steel: Approx. 6.5 N/mm²

Recommended substrate: Steel

Application: Cylindrical fitting parts

These specifications are based on Henkel's current product information and technical documentation. 

Surface Preparation

For best results, the mating surfaces should be thoroughly cleaned and dried before application. Henkel recommends cleaning the internal and external surfaces with a suitable cleaning solvent.

For inactive metals or when faster curing is required, an appropriate LOCTITE activator can be used. 

Application Method

For a slip-fit assembly, apply LOCTITE 641 around the leading edge of the shaft/pin and to the inside of the mating collar or component. Assemble using a rotating motion to distribute the adhesive evenly.

For press-fit assemblies, apply the adhesive to the bonding surfaces and assemble under appropriate pressure. For shrink-fit assemblies, the adhesive can be applied before assembly while the mating component is heated to provide sufficient clearance. 

Disassembly

One of the major advantages of LOCTITE 641 is its medium-strength formulation, making it appropriate for assemblies that need servicing.

For difficult disassembly, Henkel recommends applying localized heat to approximately 250°C and disassembling while hot. 

LOCTITE 641 vs. High-Strength Retaining Compounds

LOCTITE 641 is intended for applications where retention and serviceability are both important. If an assembly is not expected to be dismantled and requires substantially higher retaining strength, a different LOCTITE retaining compound may be more appropriate depending on the component materials, clearance, temperature and load conditions.