Loctite 243 is the industry-standard medium strength blue threadlocker designed to prevent loosening of bolts, nuts, and threaded fasteners caused by vibration, shock, and thermal cycling. Oil tolerant formula works on lightly oiled parts — no perfect cleaning required. Removable with standard hand tools for servicing.
The world's most trusted medium-strength threadlocker — proven in automotive, industrial, and marine applications for over 50 years.
Loctite 243 fills the gaps between thread flutes and cures to a tough, thermoset plastic that locks threads solid. Prevents self-loosening from vibration, shock, and thermal cycling — the #1 cause of fastener failure.
Unlike standard threadlockers that require perfectly clean, oil-free surfaces, Loctite 243's oil tolerant chemistry cures reliably on lightly oiled parts — saving time on surface preparation in real-world workshop conditions.
Medium strength means fasteners can be disassembled using standard hand tools when servicing is required. No heat, no special equipment — just a normal spanner or socket. The ideal balance of security and serviceability.
Withstands continuous temperatures from -55°C to +180°C. Ideal for automotive engines, brake systems, exhaust components, and industrial machinery that experience extreme thermal cycling.
As well as locking threads, Loctite 243 seals the thread interface to prevent leakage of fluids and gases through the thread path. Dual-purpose locking and sealing in one application.
The cured threadlocker fills microscopic gaps between threads, preventing moisture ingress and crevice corrosion. Keeps fasteners in optimal condition even in harsh, damp, or salt-water environments.
Quick, simple application — professional results every time.
Clean threads to remove heavy oil, grease, or dirt. Unlike standard threadlockers, Loctite 243 tolerates light residual oil — so perfect cleaning isn't essential. For best results, use Loctite SF 7063 cleaner.
Apply a few drops of Loctite 243 to the bolt or stud threads. For through-holes, apply to the engagement area. For blind holes, apply to both the fastener and the hole threads for complete coverage.
Assemble and tighten to the specified torque. The threadlocker cures in the absence of air and presence of metal ions (anaerobic cure). Handling strength in 10 minutes, full strength in 24 hours at room temperature.
Henkel specification data — the numbers that make Loctite 243 the industry standard.
The essential specifications at a glance.
Loctite 243 is the go-to threadlocker for a vast range of industries and uses.
How 243 compares to other Loctite threadlockers — so you choose the right one.
Everything you need to know at a glance.
| Specification | Details |
|---|---|
| Product Name | Loctite 243 Thread Lock |
| Brand | Henkel Loctite |
| Product Number | 243 |
| Volume | 50ml |
| Colour | Blue |
| Strength | Medium |
| Type | Anaerobic Threadlocker |
| Oil Tolerant | Yes |
| Removability | Removable with standard hand tools |
| Recommended Bolt Size | M5 to M24 |
| Temperature Range | -55°C to +180°C |
| Fixturing Time (23°C) | 10 minutes |
| Full Cure Time (23°C) | 24 hours |
| Breakaway Torque (M10) | Approx. 12 Nm |
| Viscosity | Thixotropic (non-drip) |
| Specific Gravity | Approx. 1.05 |
| Flash Point | >93°C |
| Gap Filling | Up to 0.13mm |
| Shelf Life | 24 months from manufacture (unopened) |
| Storage | Store at 2–8°C for maximum shelf life |
| UK Delivery | Free Royal Mail Tracked Delivery |
Loctite 243 is the world's most trusted medium-strength blue threadlocker, manufactured by Henkel and used by automotive, industrial, marine, and maintenance professionals across the globe. This 50ml bottle provides excellent value for workshops, garages, and DIY enthusiasts who need reliable vibration-resistant thread locking on a regular basis.
As an anaerobic adhesive, Loctite 243 cures in the absence of air and the presence of metal ions. It fills the microscopic gaps between thread flutes and hardens into a tough, thermoset plastic that locks the fastener in place — preventing self-loosening caused by vibration, shock loads, and thermal cycling. The medium strength formulation means the bond can be broken using standard hand tools when disassembly is required for servicing or maintenance.
Choosing the right Loctite threadlocker is critical. Loctite 243 (blue) is the ideal all-rounder — medium strength that prevents loosening but allows removal with hand tools. Loctite 263 (red) is a high-strength permanent threadlocker that requires heat for disassembly — suitable for fasteners that should never come apart. Loctite 222 (purple) is a low-strength threadlocker for very small fasteners (M2–M12) that need frequent adjustment. For 90% of workshop and maintenance applications, Loctite 243 is the correct choice.
Standard anaerobic threadlockers require perfectly clean, oil-free surfaces to cure properly. In real-world workshop conditions, fasteners are often lightly oiled from manufacturing, handling, or assembly lubricants. The Loctite 243 oil tolerant formula is engineered to cure reliably even in the presence of light surface oil — meaning less time spent cleaning and more time spent assembling. This makes it the preferred choice for maintenance engineers and mechanics who work in conditions where perfect surface preparation isn't always practical.
With an average rating of 4.8 out of 5 stars from over 2,346 reviews, Loctite 243 is the UK's most trusted threadlocker. Mechanics, engineers, and DIY enthusiasts consistently praise the reliable cure, the oil tolerance, and the confidence of knowing their fasteners won't vibrate loose. Many reviewers state they wouldn't use anything else — "if it says Loctite on the bottle, it works."
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The industry standard threadlocker — trusted by professionals worldwide. Order your Loctite 243 today.