Overview
Loctite Grade A (also known as Loctite 088 Grade A) is a red, high strength, low-viscosity anaerobic threadlocker formulated to wick into fine threads, especially on pre-assembled or close-tolerance fasteners. It cures in the absence of air between metal surfaces to form a tough thermoset plastic that locks and seals the thread interface.
Once cured, Loctite Grade A:
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Prevents loosening from shock, impact and continuous vibration
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Seals the helical thread path against fluid and gas leakage
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Protects engaged threads from corrosion and fretting over time
Key advantages:
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High-strength, permanent locking
Designed as a high-strength threadlocker, Grade A is used where fasteners must not back off in service. Disassembly of larger fasteners normally requires heat plus high torque, making it suitable for safety-critical and high-value machinery. -
Wicking into pre-assembled fine threads
With a very low viscosity (around 10–25 cP), Grade A is a wicking grade product that can be applied at the joint after assembly; it penetrates fine threads by capillary action and cures in place. -
Excellent for fine threads and small clearances
Optimized for fine-thread nuts, bolts and studs, it flows easily into tight clearances where thicker grades might not fully wet the surfaces. -
Heat-removable for overhaul
Although high strength, Grade A can be removed with localized heating up to about 315 °C (600 °F), allowing major overhauls without destroying hardware when proper tools and procedures are used. -
Qualified and QC-friendly
It complies with MIL-S-22473E Grade A and related specifications and is fluorescent under UV light, making it easy for inspectors to verify application.
Typical Applications
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Locking and sealing fine-thread nuts, bolts and studs in:
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Aircraft and aerospace hardware
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Precision machinery and instrumentation
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Hydraulics, pneumatics and fluid handling systems
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Fasteners where access after assembly is limited, but you can apply threadlocker at the edges and let it wick in
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Applications governed by MIL-S-22473E or similar aerospace / defense specs
Loctite Grade A is intended for metal-to-metal threaded joints and not recommended for plastics or pure oxygen / strong oxidizer service.
How to Use Loctite Grade A
A. Standard application (before assembly)
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Clean
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Remove loose rust, scale and old threadlocker.
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Wipe off heavy grease and thick oils (light films may remain).
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Apply
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Shake bottle.
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Apply a continuous bead along male threads, or a ring into the female threads for blind holes.
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Assemble
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Assemble parts and tighten to the specified torque.
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Do not repeatedly back off and re-torque after fixturing begins.
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Cure
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Allow to reach handling strength, then up to 24 hours at room temperature for full cure (depending on substrate and gap).
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Wicking application
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Assemble and torque the fastener to final position.
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Apply Loctite Grade A around the joint, at the nut/bolt interface or thread exit.
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Allow time for the low-viscosity liquid to wick into the threads by capillary action.
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Leave undisturbed until cured before exposing to full load or vibration.
Disassembly
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For small fasteners, strong hand tools may be sufficient.
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For larger or long-serving fasteners, heat the joint up to approximately 315 °C (600 °F) to soften the adhesive, then loosen while hot with appropriate tools.
Safety & Handling
Based on typical SDS information for Loctite 088 / Grade A:
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May cause skin and eye irritation; may cause sensitization in some individuals.
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Vapors or mists can cause mild respiratory irritation in poorly ventilated areas.
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Uncured product may be harmful to aquatic life if released uncontrolled.
Good practice
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Use in well-ventilated areas.
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Avoid skin and eye contact; wear gloves and safety glasses.
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Wash hands after handling and before eating or drinking.
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Do not pour uncured product into drains or waterways.
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Store in a cool, dry place below the recommended storage temperature (often <38 °C), in the original, tightly closed container.
Always follow the latest Henkel SDS for Loctite Grade A for your region.
FAQs
Q1: What is Loctite Grade A used for?
Loctite Grade A is a high-strength wicking threadlocker used to lock and seal fine-thread nuts, bolts and studs, especially where vibration and leakage are concerns and where pre-assembled joints need post-application locking.
Q2: How is Grade A different from common red grades like Loctite 271 or 262?
Grade A offers similar high-strength threadlocking, but with a much lower viscosity so it can wick into fine or pre-assembled threads. 271/262 are higher-viscosity reds typically applied before assembly on standard thread clearances.
Q3: Is Loctite Grade A removable?
Yes, but it is considered permanent in normal service. Removal of larger fasteners usually requires localized heating up to about 315 °C (600 °F) plus high torque with appropriate tools.
Q4: What fastener sizes are best for Grade A?
Loctite Grade A is suited to fine threads in the small-to-medium range (e.g. up to ~12 mm / ½”), particularly where clearances are small and wicking behavior is beneficial.
Q5: Can Loctite Grade A be used on stainless steel or plated fasteners?
Yes. It can be used on most common metals, including stainless and plated hardware, but cure can be slower on passive metals; allow adequate cure time before applying full load.
Q6: Is Grade A oil-tolerant?
It can cure through light oil films, but heavy layers of oil, grease or anti-seize should be removed for reliable performance, especially in critical or high-temperature applications.
Q7: Can I use Loctite Grade A on plastic threads?
No. Like other anaerobic threadlockers, Grade A is formulated for metal-to-metal joints and may cause stress cracking in some plastics; it also does not cure properly on non-metallic surfaces.
