Threadlocker Selection: Loctite 243 vs 263 vs 577

Threadlocker is one of the simplest locking methods, but choosing the wrong grade means either it won't hold or you'll never disassemble again.

How Anaerobic Threadlocker Works

Anaerobic adhesive stays liquid in air. Applied to threads and tightened, it fills the thread gaps — deprived of oxygen and catalyzed by metal ions, it cures. No micro-slip between threads = no loosening.

Common Grades

Low strength (e.g., 222): Removable with standard tools. For small threads (M6 and below), set screws, molds. Not for critical joints.

Medium strength (e.g., 243): Removable with standard hand tools. M6–M20 general purpose, pumps, motors, assembly. The most commonly used grade.

High strength (e.g., 263/271): Requires heat (200°C+) to remove. Permanent joints, severe vibration, positions never intended for disassembly.

Sealant (e.g., 577): For flange face sealing, not thread locking. Hydraulic flanges, pipe fittings. Thixotropic — doesn't run.

Application Tips

1. Threads must be clean (oil-free) — oil prevents curing

2. Apply 2–3 drops on the threads; don't coat the whole circumference

3. Fixture time: ~30 minutes; full cure: 24 hours

4. For M20+ threads, use the large-gap grade (263 instead of 243)

5. On stainless or aluminum, use activator primer for faster cure

Common Mistakes

• Using high-strength where future disassembly is needed — impossible to remove
• Applying too much — excess squeezes out and contaminates other parts
• Applying over oil — weak bond
• Loading immediately — adhesive hasn't cured

Toprecision can supply bolts pre-coated with micro-encapsulated threadlocker — long shelf life, ready to use.