Loctite 638

Loctite 638, a high-strength, high-viscosity retaining compound designed for bonding cylindrical fitting parts. It is specifically engineered for parts with bond gaps up to 0.25 mm (0.01") and offers fast curing on various metals. 

Key Features

• High Strength: One of the strongest retainers Loctite produces, designed to withstand heavy loads and prevent loosening from shock and vibration.
• Rapid Cure: Achieves a fixture time on steel in approximately 4 minutes.
• Oil Tolerant: Capable of bonding through minor surface contaminants, including cutting and industrial oils.
• Versatile Substrates: Works on both active metals (like mild steel) and passive substrates (such as stainless steel or plated surfaces).
• Temperature Range: Operates effectively from -55°C to +180°C. 

Typical Applications

Loctite 638 is commonly used for:

• Securing bushings and sleeves into housings.
• Locking gears, pulleys, and sprockets onto shafts.
• Bonding worn bearing housings to prevent rotation.

Application Instructions

1. Preparation: Clean and degrease all internal and external surfaces with a solvent like Loctite SF 7063.
2. Assembly:
   • Slip Fits: Apply adhesive to the leading edge of the male part and the inside of the female part. Rotate during assembly to ensure even coverage.
   • Press Fits: Apply thoroughly to both surfaces and assemble at a high press-on rate.
3. Curing: Avoid disturbing the parts until handling strength is reached. Full cure typically takes 24 hours at room temperature.
4. Disassembly: Apply localized heat (approx. 250°C/500°F) and disassemble while hot.