The Ultimate Guide to LOCTITE 290: The Magician’s Wand for Threadlocking

If you’ve ever spent hours meticulously calibrating a machine, only to have a tiny set screw come loose and throw everything into chaos, you know the unique frustration of vibrational forces. You’ve probably also reached for a threadlocker, only to realize you have to completely disassemble the assembly to apply it.

What if there was a solution that could fix that problem without taking everything apart? What if you could stop a leak in a porous casting without a major teardown?

LOCTITE 290. This isn’t your average threadlocker. It’s a specialized tool that feels a bit like a magician’s trick. In this deep-dive review, we’re going to move beyond the datasheet and explore why this green liquid is a secret weapon for maintenance pros, engineers, and serious DIYers.

What is LOCTITE 290? The “Wicking” Wonder

At its core, LOCTITE 290 is a medium-to-high strength, green, anaerobic threadlocker. But those technical terms don’t capture its true magic. Its defining characteristic is two-fold:

• Low Viscosity: It’s a very thin, watery liquid.
• Wicking/Capillary Action: This is the star of the show. Due to its low viscosity, LOCTITE 290 can be applied after assembly. It will willingly crawl (or “wick”) into the microscopic gaps between already engaged threads, drawn in by capillary action like water into a paper towel.

So, what is LOCTITE 290 used for? Primarily, it’s designed for:

• Securing pre-assembled fasteners: Think set screws on pulleys or gears, grub screws on couplings, and adjustment screws that you’ve already perfectly positioned.
• Porosity sealing: Filling microscopic holes and cracks in welds, castings, and powdered metal parts to prevent fluid or gas leaks.
• General threadlocking: For any application where you want a permanent, vibration-resistant lock but value the ability to disassemble with standard tools and a bit of heat.

Is LOCTITE 290 Permanent? Unpacking the “Permanent” Label

This is a crucial question. In the world of threadlockers, “permanent” is a relative term. LOCTITE 290 is classified as a medium-high strength threadlocker. Let’s break down what the datasheet tells us:

• Breakaway Torque (10 N·m / 90 lb.in): This is the torque required to initiate movement on a stationary, cured fastener. It’s a high value, meaning it creates a very strong bond that won’t be defeated by vibration.
• Prevail Torque (29 N·m / 260 lb.in): This is the torque required to continue unscrewing the fastener after breakaway. It’s significantly higher, indicating a tough, durable lock.

So, is it permanent? For all practical purposes in a vibrating, load-bearing application, yes. It will not come loose on its own. However, it is not un-demountable. The datasheet clearly states that disassembly is achievable with standard hand tools. For stubborn fasteners, applying localized heat to around 250°C (480°F) will break down the cured adhesive, allowing for easy removal.

Verdict: It’s a “serviceable permanent” lock. It’s designed to stay put until you decide, with intent and the right tools, to remove it.

The Real-World Case Studies: Where LOCTITE 290 Saves the Day

Let’s move from theory to practice. Here are some scenarios where 290 is the only logical choice.

Case Study 1: The Wobbly CNC Drive Pulley

A manufacturing plant has a critical CNC machine where the motor pulley is secured to the shaft with a set screw. Over time, vibration causes the set screw to loosen, leading to inaccurate cuts and downtime. Disassembling the motor and shaft to apply a standard threadlocker would take 4 hours of production time.

• The 290 Solution: With the machine off, a technician simply applies a few drops of LOCTITE 290 at the junction of the set screw and the pulley. The green liquid wicks down the threads instantly. After the recommended cure time, the set screw is locked in place permanently. Total Downtime: 10 minutes.

Case Study 2: The Leaky Engine Block Casting

An automotive restorer is working on a classic engine. After machining, they discover a tiny, subsurface porosity leak in the water jacket of the cast iron block. The traditional fix would be a costly and invasive welding repair.

• The 290 Solution: Following the datasheet’s “Porosity Sealing” instructions, they clean the area, apply localized heat to about 121°C (250°F), let it cool to 85°C (185°F), and then apply LOCTITE 290. The heat thins the adhesive further and pulls it deep into the pores via capillary action. As it cools and is confined in the metal pores, it cures, creating a perfect, pressure-resistant seal from the inside out.

Case Study 3: The Agricultural Adjuster

On a large piece of farm equipment, a critical plow depth adjustment mechanism uses a large bolt that needs to be strong but adjustable during seasonal maintenance. Using a red, high-strength threadlocker would make seasonal adjustments a nightmare.

• The 290 Solution: The farmer uses LOCTITE 290 during assembly. It provides more than enough strength to withstand the brutal vibrations of the field for the entire season. When it’s time to adjust, a longer wrench provides enough torque to break it loose, and a bit of heat from a torch makes it even easier. It offers the perfect balance of strength and serviceability.

The Nitty-Gritty: Curing Performance and How to Get it Right

This is where many users go wrong. LOCTITE 290 is an anaerobic adhesive, meaning it cures only in the absence of air between tight metal surfaces. The datasheet provides incredibly useful graphs that we can translate into plain English.

How long does it take for LOCTITE 290 to cure?

• Fixture Time (~20 minutes): This is when it starts to gel and hold parts in place. Don’t apply load before this.
• Handling Strength (1-2 hours): You can typically move the assembly without the screw falling out.
• Full Cure (24 hours): It reaches its maximum strength. The torque values in the datasheet are all measured after 24 hours at 22°C (72°F).

But it’s not that simple. The cure speed is a dance between Material, Gap, and Temperature.

• Material Matters: It cures fastest on active metals like steel and brass. It cures slower on passive metals like stainless steel and zinc dichromate because these metals naturally resist the chemical reaction that kicks off the cure.
• Gap is Critical: The ideal gap for anaerobic cure is less than 0.15 mm. The smaller the gap, the faster and stronger the cure. This is usually perfect for standard threaded fasteners.
• Temperature is Key: At a chilly 5°C (41°F), cure will be very slow. At a warm 40°C (104°F), it will be significantly faster.

Pro Tip: The Activator Supercharger
If you’re working with stainless steel, large gaps, or in cold conditions, the cure can be unacceptably slow. This is where Activators (like SF 7471 or SF 7649) come in. A quick spray of activator on the threads before assembly (or application for wicking) acts as a primer, providing the chemical “kick” needed for a rapid cure. The datasheet shows that with an activator, you can achieve a significant portion of the strength in just minutes instead of hours.

Head-to-Head: Loctite 290 vs. The Competition

LOCTITE 290 vs. LOCTITE 243 (Blue – Medium Strength)

• 243: The general-purpose, all-star blue threadlocker. It requires application to the bolt before assembly. It’s oil-tolerant and great for most applications.
• 290: The specialist. Its sole advantage is post-assembly wicking. If you don’t need to wick, 243 is often the more versatile choice. Strength-wise, they are in a similar class, but 290 often tests slightly higher.

LOCTITE 290 vs. LOCTITE 277 (Red – High Strength)

• 277: This is a true “permanent” red threadlocker. It’s designed for parts you never intend to take apart. Its strength is significantly higher than 290’s.
• 290: While strong, 290 is not in the same league as 277 for sheer strength. The key difference is serviceability. 277 requires extreme heat (often > 250°C) to disassemble, while 290 can often be disassembled without it. Choose 277 for permanent mounting of bearings or sleeves; choose 290 for serviceable, high-vibration fasteners.

LOCTITE 290 Equivalent

While Henkel/Loctite is the market leader, other brands offer similar wicking threadlockers. Permabond offers anaerobic adhesives with wicking capabilities, and you might find generics labeled as “Green Wicking Grade Threadlocker.” Always check the technical data to ensure the viscosity and strength specifications match your needs.

Final Verdict: Who Should Keep a Bottle of LOCTITE 290 in Their Toolbox?

LOCTITE 290 is not a replacement for your everyday blue 243. Instead, it’s a specialized problem-solver. You should seriously consider it if:

• You work on machinery with set screws or pre-assembled components.
• You deal with leaks in porous metal castings or welds.
• You need a high-strength threadlocker but value the ability to perform field service without a blowtorch.
• You’ve ever said, “I wish I didn’t have to take this apart to lock it.”

Its unique wicking ability turns a major, time-consuming disassembly job into a 30-second fix. That’s not just a convenience; it’s a massive cost and time savings. While the Loctite 290 price is higher than standard threadlockers, its value is realized not in the bottle, but in the hours of labor it saves on a single job.

In conclusion, LOCTITE 290 is more than just an adhesive; it’s a paradigm shift in maintenance and assembly. It’s the clever solution that keeps the wheels turning, literally and figuratively. Keep a 50ml bottle on hand for small jobs, and you’ll soon find it’s one of the most valuable tools in your kit.