If you’ve ever dealt with fasteners vibrating loose on hydraulic equipment, you’ll know how frustrating—and dangerous—it can be. This is exactly where thread locking adhesive comes into its own. The simplest way to think of it is as a liquid lock washer that chemically bonds threads together, stopping them from self-loosening under vibration, temperature shifts, and shock.
What Is Thread Locking Adhesive and Why Does It Matter?
In high-stakes industrial and mobile environments, a single loose fastener isn’t just a minor issue; it’s a critical point of failure. Vibration is a constant force in everything from agricultural machinery to mobile plant equipment, and it can relentlessly work threaded assemblies loose. This self-loosening can lead to dangerous fluid leaks, unexpected and costly downtime, and very real safety hazards.
A thread locking adhesive tackles this problem head-on. It’s a specialised, single-component adhesive that you apply as a liquid to the threads of a nut or bolt just before you tighten it. Once assembled, it cures into a tough, solid plastic that completely fills the microscopic gaps between the mating threads.
More Than Just a Glue
This process does far more than just stick threads together. The solid polymer forms a powerful mechanical lock, resisting vibrational loosening much more effectively than old-school methods like spring washers or castellated nuts. On top of that, it creates a complete seal, protecting the threads from moisture, corrosion, and the ingress of hydraulic fluids.
This dual function of locking and sealing is what makes thread locking adhesive so invaluable for MRO teams and design engineers. It turns a standard fastener into a reliable, sealed, and locked component, which massively boosts the overall integrity of your equipment. The consequences of not using it can be severe. In the UK hydraulic and industrial sectors, these adhesives are indispensable for preventing fastener failures. In fact, UK Health and Safety Executive (HSE) data shows that mechanical failures accounted for 18% of reportable injuries in manufacturing and agriculture, with loose bolts contributing to over 12,000 incidents annually. Many of these could have been prevented with a reliable thread locker. You can learn more about the market impact of these adhesives and their role in improving industrial safety.
Here’s a simple way to think about it: A mechanical locker, like a split washer, applies tension to try and stop a fastener from loosening. A thread locking adhesive eliminates the very possibility of movement by filling the empty space where movement could begin in the first place.
The Anaerobic Advantage
The science behind this transformation is actually quite clever. Most thread lockers are anaerobic adhesives. This simply means they stay liquid as long as they’re exposed to oxygen (like when they’re in the bottle) but start to cure, or harden, only when deprived of air and in the presence of metal ions.
When you tighten a bolt coated with the adhesive, you squeeze out the air. That action is the trigger for the chemical reaction. This unique property ensures the product won’t cure before you’re ready, giving you all the time you need to assemble components correctly. It’s a smart chemical process designed specifically for the unique environment inside threaded fasteners, making it completely different from any other type of glue or epoxy.
The Science Behind How Anaerobic Adhesives Work
Have you ever wondered how a bottle of thread locking adhesive can sit on a shelf as a liquid for months, yet set like concrete just minutes after you apply it to a bolt? It’s not magic, but it is clever chemistry. The secret is something called an anaerobic cure, a process that’s perfectly suited for the tight, airless environment inside a threaded fastener.
While the adhesive is in the bottle, you can think of it as being in a state of suspended animation. The special semi-translucent plastic of the container actually lets a tiny amount of oxygen through, and this oxygen stops the chemical curing process in its tracks. As long as it can ‘breathe’, it stays liquid and ready to go. The reaction only kicks off when those conditions change.
The Two Triggers for Curing
For an anaerobic adhesive to go from a liquid to a solid, two things need to happen at the same time. This elegant, built-in safety mechanism is why it only hardens exactly where and when you want it to.
- The Absence of Oxygen: When you apply the liquid to a bolt’s threads and tighten the nut, you squeeze out all the air. Removing oxygen is the first critical trigger that ‘wakes up’ the adhesive.
- The Presence of Metal Ions: The adhesive also needs to touch a metal surface. Metal ions act as a catalyst, kicking off and speeding up the polymerisation process. This is the second trigger.
If you don’t have both of these conditions, nothing happens. The adhesive just stays liquid. That’s why a drop of thread locker spilled on a plastic workbench will never harden, but the same drop inside a tightened steel nut and bolt assembly cures solid.
A great way to think about it is like a two-key safety system. You have to turn both keys at once to launch. For a thread locker, cutting off the air supply is the first key, and contact with metal is the second.
From Liquid to Solid Polymer
Once both triggers are pulled, a chain reaction called polymerisation begins. The small, individual molecules (monomers) in the liquid start linking up to form incredibly long, strong chains (polymers). This process is what transforms the liquid into a tough, cross-linked thermoset plastic.
This isn’t like household glue that dries through evaporation. This is a fundamental chemical change, and it’s what gives thread lockers their incredible strength. The cured plastic doesn’t just stick the threads together; it fills every microscopic void between them. The result is a single, unitised assembly that can stand up to shock and vibration far better than any mechanical locking device.
This unique anaerobic science is what sets thread locking adhesive apart. Epoxies need you to mix two parts, and super glues (cyanoacrylates) cure using moisture in the air. Anaerobic adhesives, on the other hand, are designed specifically for the airless, metallic world of a threaded fastener, making them the perfect locking and sealing solution for demanding hydraulic systems.
For expert advice on your specific application or to source the right components for your needs, phone 01724 279508 today, or send us a message at https://www.mahydraulics.co.uk/contact-us/.
How to Choose the Right Grade of Thread Locker
Picking the right thread locking adhesive is more than just grabbing a bottle off the shelf. It’s a crucial decision that directly affects how reliable your assembly will be and, just as importantly, how easy it will be to service down the line.
Get it wrong, and you’re in for a world of pain. A grade that’s too strong can turn a simple maintenance job into a battle with a blowtorch and breaker bar. On the other hand, one that’s too weak completely undermines the point of using it in the first place. Thankfully, the industry uses a simple colour-coding system to keep things straightforward.
It’s all about finding that sweet spot between locking strength and removability. You need to match the product to the job at hand, whether you’re securing a tiny adjustment screw or a hefty structural bolt on a hydraulic press.
Low Strength (Purple): The Gentle Holder
When you see a purple thread locker, think delicate. This low-strength grade is designed for small fasteners, typically under 6mm in diameter. We’re talking about the adjustment screws on control valves, calibration points on gauges, or small set screws that need to be held in place against vibration but still allow for easy fine-tuning.
Its breakaway torque is minimal, so you can undo the fastener with a simple hand tool without any fear of snapping it.
- Best For: Small diameter screws (M2 to M6).
- Typical Use: Securing adjustment screws on hydraulic control valves or locking set screws in instrumentation panels.
- Removal: A standard screwdriver or Allen key will do the job with very little effort.
Medium Strength (Blue): The Everyday Workhorse
The blue stuff is the one you’ll find in almost every technician’s toolbox, and for good reason. It’s the most versatile thread locking adhesive out there, providing excellent vibration resistance for fasteners ranging from 6mm up to around 20mm.
This grade is the perfect all-rounder. It’s strong enough to confidently lock and seal nuts and bolts on pumps, motors, and hydraulic fittings, yet it’s still considered “removable.” That means you can disassemble the joint with standard hand tools when it’s time for maintenance. Its versatility makes it the go-to for countless jobs. Of course, proper thread identification is still vital to ensure a perfect match.
Think of blue thread locker as your default choice. If a fastener needs to be secure but also needs to be serviced from time to time, this is almost always the right one to reach for.
High Strength (Red and Green): The Permanent Bond
When a fastener absolutely, positively cannot come loose, you bring in the heavy hitters: the high-strength grades. These are typically red for general high-strength applications and green for wicking into parts that are already assembled.
Red thread locker is essentially a chemical weld. It’s built for permanently locking large studs and bolts (up to 25mm and larger) on assemblies that aren’t meant to be taken apart. This is what you’d use for mounting studs on a hydraulic motor, frame bolts, or ring gears. To get these apart, you’ll need to apply localised heat of around 250°C to soften the polymer before you can even think about putting a spanner on it.
Green thread locker is a bit different. It has a very low viscosity, almost like water, which allows it to “wick” deep into the threads of pre-assembled fasteners through capillary action. If you’ve got a component that’s already been torqued down but you realise it needs securing, a few drops of green at the join will seep in and lock it solid.
Thread Locking Adhesive Strength Selection Guide
To make things even clearer, here’s a quick-reference table comparing the common grades you’ll encounter in UK hydraulic and industrial work.
| Grade / Colour | Strength & Breakaway Torque | Typical UK Hydraulic Applications | Viscosity | Removal Method |
|---|---|---|---|---|
| Purple | Low / 6-10 Nm | Small adjustment screws, fasteners on gauges, set screws. | Low | Standard hand tools. |
| Blue | Medium / 15-30 Nm | Pump housing bolts, valve cover fasteners, motor mount bolts. | Medium | Standard hand tools. |
| Red | High / 25-45 Nm | Cylinder block studs, frame bolts, permanent bearing mounts. | Medium | Requires heat (approx. 250°C). |
| Green | Medium-High / 10-25 Nm | Securing pre-assembled fasteners, electrical connectors. | Very Low | May require heat. |
Getting the grade right is the foundation of a successful application. By understanding these simple colour codes, engineers and technicians can ensure every single fastener performs exactly as it should—securely, reliably, and serviceably.
Key Factors for Choosing the Right Adhesive in Hydraulic Systems
Picking a thread locking adhesive isn’t as simple as grabbing the first bottle you see. When you’re dealing with the pressures and demands of a hydraulic system, you need to dig a bit deeper than just the strength grade. If you skip over the finer details of the working environment, you’re risking an unexpected failure down the line, even with what seems like the “correct” product.
Think about it: an adhesive that works perfectly in a clean, stable workshop might completely break down when faced with the heat, vibration, and aggressive fluids of mobile plant or industrial machinery. Getting this right is about good engineering, not just guesswork.
Will It Stick to Your Metal?
Not all metals play nicely with anaerobic adhesives. The magic of these liquids is in the curing process, and the speed and strength of that cure depend entirely on the type of metal you’re working with. Metals are basically split into two camps: active and inactive.
- Active Metals: These are the easy ones. Surfaces with high iron or copper content—think steel, iron, copper, and brass—are natural catalysts for the adhesive. The cure happens fast, and you’ll get the full strength the manufacturer promised.
- Inactive Metals: These materials are a bit more stubborn. Stainless steel, aluminium, titanium, and zinc-plated parts lack the metal ions needed to kick off a strong, fast cure. The adhesive will cure much more slowly and might never reach its full potential strength.
The fix is simple: use a primer or activator. It’s a solvent-based liquid you apply to the threads first. This leaves behind a thin layer of copper ions, essentially tricking the adhesive into thinking it’s on an active surface. The result is a fast, reliable, full-strength cure.
Heat and Vibration: The Real-World Test
Hydraulic systems rarely operate in a gentle environment. They’re often tucked in next to hot engines or running in high-friction industrial settings, which means they get hot. It’s vital to choose a thread locker with a temperature range that can handle the heat. A standard product might top out at around 150°C, but specialist high-temperature formulas can withstand over 230°C. Go past that limit, and the polymer will soften, putting the joint at risk.
Vibration is the other constant enemy. It’s notorious for working fasteners loose, and in the UK, it’s a major headache for agricultural and mobile machinery. A recent industry analysis showed a shocking number of tractor and harvester breakdowns in England were down to failed fasteners, costing farmers millions. In trial fleets where thread lockers were properly used, these incidents dropped dramatically. You can read more about the industrial impact of these adhesives and how they keep machinery running.
Pro Tip: Always check the Technical Data Sheet (TDS) for any adhesive you’re considering. It’s not just marketing fluff—it gives you the hard numbers on maximum operating temperatures and other performance data you need to choose the right product for the job.
Chemical Resistance and Filling the Gaps
Your chosen adhesive must be able to hold its own against whatever it’s swimming in. Most anaerobic adhesives are brilliant at resisting oils, glycols, and hydrocarbon-based fluids. But if your system uses more specialised synthetic fluids, it’s always worth double-checking the compatibility.
Finally, think about the gap you need to fill, which comes down to the adhesive’s viscosity—basically, how thick or runny it is. For fine threads, you want a low-viscosity (thin) liquid that can wick its way into tiny spaces. For coarse or even slightly damaged threads, you need a high-viscosity (thicker) gel that can fill larger voids without running out. Using a thin liquid on a big gap will leave you with an incomplete bond and a potential leak path. The same logic applies when you’re adapting fittings, like a 1/4 BSP to metric fitting, where thread pitch and size are key.
By taking a moment to consider these factors—materials, temperature, vibration, chemical exposure, and gap size—you can select a thread locking adhesive that will give you a rock-solid, reliable joint every time.
For expert help sourcing hydraulic parts for your specific setup, give us a call on 01724 279508, or send us a message online.
Getting it Right: Best Practices for Application and Removal
Getting a perfect bond with a thread locking adhesive is about more than just picking the right colour bottle. It all comes down to the process. Nailing the application—and knowing how to reverse it when needed—is what separates a rock-solid, reliable joint from one that’s just waiting to fail. Proper technique is what unlocks the full potential of these amazing adhesives.
This flowchart breaks down the critical thinking that goes into choosing the right product for the job.
As you can see, factors like the material you’re working with, the temperatures it’ll face, and even the tiny gaps between the threads all play a huge part. To get consistent results, it’s vital to document your procedures clearly. If you want your team to follow the same steps every time, this guide to creating a step-by-step guide has some great tips on making instructions easy to follow.
Perfecting the Application Process
Think of any contamination as the sworn enemy of a good adhesive bond. The journey to a perfect assembly always, always starts with clean surfaces. Any lingering oil, grease, or grime will get in the way of the anaerobic reaction and compromise the entire joint.
- Clean and Degrease: First things first, get both the male and female threads spotless. A good industrial degreaser and a wire brush are your best friends here. Scrub away every last trace of oil, dirt, and any old adhesive. Then, make sure the parts are bone dry before you move on.
- Prime if Necessary: As we mentioned earlier, those less reactive (inactive) metals like stainless steel or aluminium need a helping hand from a primer. Apply a thin, even coat to both sets of threads and give it a minute or two to dry before reaching for the adhesive.
- Apply the Adhesive: How you apply it depends on the type of hole you’re dealing with.
- For Through-Holes: Put a few drops of the thread locker onto the bolt right where the nut will eventually sit.
- For Blind Holes: Drip a few drops down into the bottom of the female threads. When you screw in the bolt, the trapped air cleverly pushes the adhesive upwards, coating the threads on its way out.
- Assemble and Torque: Get the parts together straight away and tighten them to the manufacturer’s specified torque. The clock starts ticking on the curing process as soon as the air is gone, so don’t hang about. On certain components, like a quick release coupler hydraulic fitting, hitting the right torque is absolutely critical for safety.
Key Takeaway: You don’t need to drown the threads. A little goes a long way. Overdoing it is just wasteful and risks the excess goo migrating into places you really don’t want it.
How to Safely and Effectively Get it Apart Again
Sooner or later, a locked fastener will need to come off for maintenance or a repair. The approach you take is dictated entirely by the strength of the adhesive holding it in place.
Removing Low and Medium-Strength Grades (Purple/Blue):
These grades are designed to be “service-removable,” so you’ll just need your standard hand tools. It’ll take a bit more force to get it moving—what we call the “breakaway torque”—but once that initial bond is broken, it should unscrew with normal effort. Your trusty spanner or socket set will do the job.
Removing High-Strength Grades (Red/Green):
Trying to beat a red or green thread locker with brute force is a one-way ticket to snapped bolts and wrecked components. These permanent grades require heat to persuade them to let go.
- Apply Localised Heat: Use a heat gun or a blowtorch to carefully heat the nut or the housing around the bolt to roughly 250°C. This is the magic temperature that softens the thermoset plastic of the cured adhesive.
- Disassemble While Hot: While the assembly is still hot, grab your tools and unscrew the fastener. You’ll find it gives way much more easily once the adhesive has been softened.
- Clean Up the Mess: After the parts have cooled down, use a wire brush and a good solvent to get rid of the old, charred adhesive from the threads before you even think about reassembling.
Troubleshooting Common Problems
Even the most careful engineer can run into a snag. Here are a couple of the most common issues and how to fix them:
- The Adhesive Won’t Cure: Nine times out of ten, this is down to dirty surfaces or trying to use it on an inactive metal without a primer. The fix? Take it apart, give everything a thorough clean and degrease, and use an activator if the material calls for it.
- The Joint Works its Way Loose: This usually points to one of three things: not enough adhesive was used, the strength grade was too low for the amount of vibration, or the assembly wasn’t torqued down properly. Double-check your coverage, your product choice, and your torque specs.
Mastering these straightforward practices turns thread locking adhesive from a simple bottle of goo into an essential engineering tool for building and maintaining robust hydraulic systems.
For specific advice on your application, give us a call on 01724 279508 today, or send us a message at https://www.mahydraulics.co.uk/contact-us/.
Your Thread Locking Adhesive Questions Answered
When it comes to using thread locking adhesives, a few questions always seem to come up with engineers, technicians, and maintenance teams. Getting the right answers is crucial for building hydraulic systems that are safe, reliable, and don’t end up costing you more down the line. Let’s tackle some of the most common queries we hear.
Can I Reuse a Bolt That Has Had Thread Locker on It?
This is a big one, and the short answer is: not without a thorough clean-up first. For a bond you can trust, you absolutely must remove every last bit of the old adhesive from both the bolt and the internal threads.
This means getting in there with a wire brush and a good solvent to dissolve any cured residue. If you leave any of the old stuff behind, it can mess with your torque readings, prevent the threads from engaging properly, and seriously weaken the new bond. It’s always best practice to start with clean threads and apply fresh adhesive every time.
What Is the Shelf Life of a Typical Thread Locker?
Most anaerobic thread lockers will last you about one to two years, provided they’re stored unopened in a cool, dark place. You might notice the bottle is only about half-full, but don’t worry—that’s by design, not a mistake at the factory.
The air in the top of the bottle is actually what keeps the adhesive from curing prematurely. Oxygen stops the chemical reaction, so that air gap is essential. Always give the expiration date a quick check before you use a bottle to make sure you’re getting full performance.
Will Thread Locking Adhesive Work on Plastic Fasteners?
Simply put, no. Standard anaerobic thread lockers are designed specifically for metal-to-metal applications. Their curing process is a bit like a two-part puzzle: it needs the absence of air and the presence of metal ions from the fastener’s surface to kick off the chemical reaction.
Because plastic doesn’t have those metal ions, the adhesive just won’t cure. If you need to lock plastic fasteners, you’ll have to look for a different solution, like a cyanoacrylate (super glue) or an adhesive specifically formulated for plastics.
Key Takeaway: Think of the metal itself as a vital ingredient in the reaction. Without it, the adhesive stays liquid, which really drives home why these products are so specialised for industrial metalwork and hydraulic systems.
How Does the Cost Compare to Mechanical Locking Methods?
At first glance, a spring washer or a lock nut might look like the cheaper option. However, when you look at the bigger picture, thread locking adhesives are often far more economical. A single bottle, which might cost you around £15-£25, can secure hundreds of fasteners, bringing the cost per application right down.
What’s more, the adhesive creates a perfect seal that protects against corrosion and stops leaks. This prevents expensive failures, cuts down on maintenance time, and means you don’t have to keep a huge inventory of different-sized mechanical parts. That reliability delivers a much better return on your investment over time.
Need Help Securing Your Hydraulic Systems?
It’s easy to see thread lockers as just another bottle on the workshop shelf, but they’re so much more than that. Think of them as the unsung heroes of your hydraulic systems, quietly working to guarantee safety, reliability, and a long operational life. Choosing the right one and applying it correctly is the difference between a smooth-running machine and one plagued by costly, unexpected downtime.
Here at MA Hydraulics, we’re not just here to sell you parts. We see ourselves as your technical partner, ready to roll up our sleeves and help you with the nitty-gritty of hydraulic system assembly, operation, and maintenance.
Our team has been in the trenches and knows what works. We can guide you through the maze of options to find the perfect thread locking adhesive for your specific challenge and help you source all the other hydraulic components you need to keep things running like clockwork.
For practical advice that’s tailored to your exact application, give us a ring on 01724 279508 or send us a message.
