Loctite 638 – this is a very high strength shaft and bearing adhesive (Retaining Compound), used for cylindrical parts with larger clearances than 603/609.
1. Product information
Name: Loctite 638 Retaining Compound.
Color: Green.
Viscosity: Medium to high (~ 2500 mPa·s).
Applications:
Fixing bearings, bushings, gears, pulleys, pins, rotors on shafts or in housings.
Suitable for clearances up to 0.25 mm (larger than 603/609/620).
Can be used on lightly oiled surfaces (no need for absolute cleaning).
Durability: Very high → disassembly requires large heating.
Working temperature: –55 °C to +180 °C.
Curing mechanism: Anaerobic (without air and in contact with metal).
2. Preparation before use
Surface cleaning: recommended to use Loctite SF 7063 to remove oil, dust, rust.
For less active metals (stainless steel, aluminum, zinc) → use Loctite Primer SF 7471 or SF 7649 to speed up curing.
Make sure the surface is dry and clean.
3. How to use
Apply glue:
Apply glue to both shaft and hole.
For bearings/bushings: apply glue to the hole and then press the shaft in.
Assemble immediately after applying, avoid leaving the glue exposed to the air for a long time.
Hold the part in place until the glue has initially cured.
4. Curing time
Initial fixation: ~ 10 minutes (steel) to 20 minutes (less active materials).
Working strength: 1–3 hours.
Maximum strength: after 24 hours at room temperature.
5. Safety notes
Wear gloves and goggles when handling.
Avoid contact with eyes, skin, mouth.
Do not use near heat/fire sources.
Store in a cool, dry place, ideal temperature 8–21 °C.
👉 Summary of the differences:
Loctite 603 / 609: small gap (0.1 mm), lower viscosity.
Loctite 620: medium gap (0.15 mm), highest heat resistance (200 °C).
Loctite 638: large gap (0.25 mm), highest strength and good oil resistance.
Do you want me to make a visual comparison table 603 – 609 – 620 – 638 for easy reference?
admin –
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