If you’ve experienced the frustration of a seemingly secure bolt vibrating loose, you might be a victim of the “Blue vs. Red” dilemma. Medium-strength threadlockers (the common “blue” formulas) are the universal go-to for hobbyists and DIYers, but their reliability has limits. Using blue threadlocker when the job explicitly demands a heavy-duty, permanent bond—a red formula—is a recipe for component loosening and potential catastrophic failure.
This common mistake is a matter of mis-specifying the load requirement. We will clarify the critical difference in strength and recommend the appropriate Incure Re-Lok™ solution to ensure your most critical assemblies stay locked down permanently.
Understanding Threadlocker Strength Grades
Threadlockers are categorized by their locking strength, which determines their resistance to loosening forces like vibration, thermal shock, and impact.
| Strength Grade | Typical Color | Purpose | Disassembly Method |
| Low | B22 Purple | Small fasteners (under 1/4″), frequent adjustment. | Hand tools only. |
| Medium | B43 Blue | General purpose, fasteners up to 3/4″ (20mm). | Hand tools (torque required). |
| High | B72/B77 Red | Permanent locking for critical, high-stress assemblies. | Requires heat (550∘F / 290∘C) and hand tools. |
The Reason Blue Fails High-Stress Applications
Medium-strength (Blue) threadlockers, like Incure Re-Lok™ B43, are designed to be removable with standard hand tools. This means the force required to break the bond is only slightly higher than the torque used to tighten the bolt.
In high-stress environments such as:
- Motor or Engine Mounts
- Suspension or Chassis Bolts
- Heavy Machinery
- Pumps and Compressors
The constant, severe vibration and cyclic stress generate forces greater than the holding power of the Blue threadlocker. Over time, these forces cause the bond to break down incrementally until the screw begins to loosen and, inevitably, falls out. The solution is simple: you need a permanent bond that cannot be broken by vibration alone.
The Incure Re-Lok™ Solution for Permanent Security
When a blue product has failed you, it’s time to upgrade to the highest level of retention. We recommend the Incure Re-Lok™ B72 Red Threadlocking Adhesive (Heavy Duty) for permanent installations where component safety is critical.
| Product | Strength | Key Feature | Ideal Applications |
| Incure Re-Lok™ B72 Red Threadlocking Adhesive (Heavy Duty) | HIGH | Resists extreme vibration, shock, and thermal cycling. Must be heated for removal. | Structural bolts, flywheel bolts, press fits, and permanently set adjusters. |
| Incure Re-Lok™ B77 Red Threadlocking Adhesive (Extreme Duty) | EXTREME | Highest strength for large bolts (up to 1″) and maximum environmental resistance. | Critical large-diameter fasteners in heavy industrial settings. |
The Right Way to Use Red Threadlocker
Because Red threadlockers are designed for a permanent bond, proper preparation is even more vital:
- Preparation is Mandatory: Always clean and degrease the male and female threads thoroughly. Any surface contamination will compromise the extreme strength you are seeking.
- Apply Precisely: Use the application technique outlined previously—apply only enough to fill the engaged thread void (typically on the leading edge of the bolt).
- Know the Removal Requirement: Understand that Incure Re-Lok™ B72 and B77 require localized heat (e.g., a heat gun or torch) to reach approximately 550∘F (290∘C) before the bond can be safely broken with hand tools. Do not use Red on components you intend to adjust frequently!
By selecting the high-strength Incure Re-Lok™ B72 or B77 and ensuring proper surface prep, you can be confident that your critical fasteners will remain locked, even when subjected to the toughest working conditions.