High Strength Retaining Compound
Product category: Retaining compounds
- Technical specifications
LOCTITE® 638 is designed for the bonding of cylindrical fitting parts, particularly with narrow bond gaps approaching 0.25 mm. The product cures when confined in the absence of air between close-fitting metal surfaces and prevents loosening and leakage due to shock and vibration. It not only works on active metals but also on passive substrates, exhibiting robust cure performance. The product offers high-temperature performance and good oil tolerance, and tolerates minor surface contaminants.
Tolerates minor contaminants, including industrial oils
High strength on all metals, including passive substrates (e.g. stainless steel)
High temperature resistance
Ideal for shafts, gears, pulleys and similar cylindrical parts
DVGW Approval (EN 751-1): NG-5146AR0619
P1 NSF Reg. No.: 123010
WRAS Approval (BS 6920): 0511518
Agency approvals / certificates / specifications:
DVGW (EN 751-1): NG-5146AR0619,NSF P1 Reg No: 123010,WRAS (BS 6920): 0511518
For Close Fitting Cylindrical Parts,For Slip Fitted Parts,Retaining
0.15 mm - 0.25 mm
Fluorescent,Oil Tolerant,Strength: High Strength,Temperature Resistant,Viscosity: High Viscosity
-55.0 °C - 180.0 °C (-65.0 °F - 355.0 °F)
Shear strength, Steel:
31.0 N/mm² (4500.0 psi)
2500.0 mPa·s (cP)
How to use
Use LOCTITE® SF 790™ to remove any old adhesive from parts. Use LOCTITE® SF 7070™ to degrease and clean surfaces prior to applying adhesive. For gaps larger than 0.5mm or worn out shafts, bearing seats or keyways, use LOCTITE® metal-filled compounds to rebuild the surfaces.
If cure speed is too slow due to passive metals (stainless steel, aluminum and plated metals) or low temperature (below 5°C), use LOCTITE® SF 7649™ activator. Allow to dry.
Apply adhesive around the leading edge of the male component and the inside of the female component. Assemble parts with a rotating motion to ensure good coverage. Wipe off excess adhesive.
Apply 360 degree beads of adhesive to both bond surfaces at the leading edges of insertion or engagement, and assemble at high press-on rates. Wipe off excess adhesive.
Apply the adhesive onto the male component; heat the female component to cause expansion for free assembly. Assemble components and allow temperatures to equilibrate. Wipe of excess adhesive.
Apply localized heat to approximately 500°F/260°C; disassemble while hot. For corroded or seized parts, use LOCTITE® 8040™ Freeze and Release.
For manual assembly of adhesive the use of LOCTITE® Pro Pump or LOCTITE® Peristaltic Hand Pump is recommended to ensure a conistent application volume. For semi-automatic or fully-automated dispensing options contact our technical service team for advice.
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.
The optimum fit for thinner/low viscosity products like LOCTITE® 609 is 0.025 mm to 0.15 mm. For thicker/high viscosity products like LOCTITE® 680, it is 0.05 mm to 0.38 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 -65°F to 300°F (-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.
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.
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.
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