Loctite 638 Equivalent: Supex 638 for High-Strength Retaining Applications
Loctite 638 is one of the most widely used retaining compounds in the industry. Known for its high strength, gap-filling capability, and resistance to temperature and chemical exposure, it is ideal for bonding cylindrical parts such as shafts, bearings, bushings, and rotors. However, due to availability, pricing, or brand preferences, many engineers and technicians seek a Loctite 638 equivalent that offers similar performance characteristics.
In this article, we’ll explore the top Loctite 638 alternative, how to choose the right one, and what factors to consider for your application.
Why Choose an Equivalent to Loctite 638?
There are several reasons professionals look for a Loctite 638 substitute:
Cost efficiency – Some alternatives offer similar performance at a lower price.
Local availability – Equivalent products may be more accessible in certain regions.
Industry preferences – Some sectors use specific brands due to OEM or certification requirements.
Project flexibility – When Loctite 638 is out of stock or has long lead times, alternatives help avoid delays.
Key Properties of Supex 638
Before choosing an equivalent, it’s important to understand what makes Loctite 638 effective:
| Property | Specification |
|---|---|
| Type | Anaerobic Retaining Compound |
| Strength | High |
| Viscosity | Medium/High (2,000–3,000 mPa·s) |
| Temperature Range | -55°C to +180°C (-65°F to +355°F) |
| Cure Time | Fixture: 5–15 min, Full: 24 hrs |
| Gap Fill | Up to 0.25 mm |
| Color | Green |
How to Choose the Right Equivalent
When selecting a Loctite 638 substitute, consider:
Application Type: Slip fit vs. press fit
Gap Size: Ensure the equivalent fills up to 0.25 mm
Strength Requirements: Choose high-strength adhesives for permanent assemblies
Operating Temperature: Match or exceed the 180°C tolerance
Availability & Brand Trust: Choose a product available in your region with good technical support
Application Tips for Retaining Compounds
Surface Prep: Clean and degrease surfaces before applying adhesive.
Primer Use: For inactive metals (e.g., stainless steel), use a primer like Loctite 7649 to speed curing.
Assembly Time: Work quickly—most equivalents start to fixture in under 15 minutes.
Storage: Store in a cool, dry place to maintain shelf life.
Always consult technical data sheets and, where possible, perform testing for your specific application.
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