5 reasons why Loctite 243 is a “must have” in your maintenance kit


Loctite 243 is a medium strength threadlocker that secures all types of threaded fasteners like nuts, bolts and studs, at the same time sealing them against corrosion. While there are naturally exceptions in some cases, Loctite 243 will be suitable for the vast majority of standard threadlocking applications and you are unlikely to need another grade very often.

Reason 1:5reasons_reason1

Strengthens threaded assemblies against vibration by adding approx. 25% to the torque needed to loosen a normally tightened bolt assembly.

Reason 2:5reasons_reason2

One product for locking various sized fasteners, versus an inventory of different sized mechanical locking devices you would otherwise need to keep (saves both money and space).

Reason 3:5reasons_reason3

It’s suitable for active and inactive substrates. Do note though that activator Loctite SF 7649 is needed on inactive surfaces.

Reason 4:5reasons_reason4

It’s tolerant to minor oil contamination, curing on as-received fasteners without cleaning, or on parts that aren’t easily accessible for thorough cleaning during maintenance.

Reason 5:5reasons_reason5

Assembly locked by Loctite 243 can be easily disassembled, when needed, using ordinary hand tools.

In case you’ve never yet tried Loctite 243, you can now request a free sample and give it a go. (Please select your respective country at the top navigation before filling in the form.)

When to use Loctite Activator with your Loctite Threadlocker


All metals are not exactly the same in their characteristics. That is a widely known fact in the engineering world. And hence, they don’t behave the same in how they interact with substances, in how they can be processed and handled etc. When it comes to bonding in general, and threadlocking specifically, there are two main types of metals to distinguish between: active and inactive metals.

Your typical active metals include iron, plain steel, copper, brass, bronze, nickel, manganese, Monel™ and Kovar™. With any one of these, in most of the typical cases, the bonding (threadlocking included) will work just fine without the use of any activator. You might still optionally use it, usually in the cases when you want to speed up the cure and achieve handling strength faster. But it will also work just fine without.

However, there’s also the other group, the inactive metals, such as (and this list is by no means exhaustive) any plated parts, anodised aluminium (i.e. Alodine® or Iridite™), titanium, stainless steel, galvanized steel, zinc, pure aluminium, cadmium, magnesium, natural or chemical black oxide, magnetite steel, Iconel™ or any of your precious metals such as silver or gold.


With these latter, it really is helpful to use the Loctite SF 7649 activatorbefore applying the threadlocker, to activate the surface and enable the adhesive to achieve the full strength quicker.

Loctite SF 7649 has drying time of 30-70 seconds. However, it has on-part life of 30 days, which means you can spray it on your parts ahead of time in a separate phase of your process and have them ready to be built in when the time for that comes.

To summarize what the activator does:

When to use activator_temp_gaps_deep thrds

  • Shortens the cure time on any type of metal
  • Activates the inactive surfaces to promote adhesion
  • Promotes adhesion in cold temperatures
  • Promotes curing / adhesion where there are larger gaps or deep threads

Feel free to visit our website for more information on Loctite Threadlockers (you can select a different language or country in the navigation at the top of the page).

Why is Loctite Threadlocker better than double nut


Coming back to mechanical locking devices for threaded assemblies, double nut is probably the most common one. Wherever the assembly design allows it, it’s the simplest thing to do: just add one more nut of the same size you already have anyway for the bolt in question.

While the second nut does increase the surface of interfaced threads, it doesn’t eliminate the gaps between them. Certainly, you can argue that it will take that much longer for the vibrational impact to shake such a bolt into loosening, but the loosening will still inevitably happen.

Additional nut increases one more thing: it doubles the amount of surface that can corrode together between the bolt and the nuts. And that’s a nasty surprise that you normally discover when you’re about to dismantle the piece.

Finally, out of all the mechanical locking devices, the nuts are the heaviest, and if you use several double nuts to secure your bolts on a piece of equipment, you definitely have to count with all the additional weight you’ve added to it. As far as elegant solutions go, this is not one of them.

If you replace the second nut by just a few drops of a Loctite Threadlocker, you’ve not only found a much more elegant solution, but you’ve really resolved the issue of vibrational loosening – permanently.

When a little bolt becomes a big problem: prevented catastrophic equipment failure in a mine


I already spoke about the holy grail of industrial maintenance – zero downtime hours – and how the cause of failures can sometimes be as trivial as a loosened bolt, which then leads to loss of productive hours and ultimately – financial losses.

But there is one loss that is above all and that nobody wants to risk – injuries and loss of lives. Which is why there should be no compromises when it comes to safety, and all maintenance engineers will unanimously agree with that.


australian mine

In an example of an Australian mining operation, loosening (and ultimately breaking off) of the M36 anchor bolts led to collapsing of concrete footings, threatening with the collapse of the jaw crusher equipment frame. The bolts had been locked by a spring washer, which simply couldn’t rise to the challenge of securing the bolts on a piece of equipment subjected to that level of severe vibration and shear forces. The bigger the bolts, the bigger the gap between the threads, which spring washers don’t even begin to tackle. And the bigger the gap, the more impact the vibration has on the assembly.

To permanently solve this problem, Loctite 277 (high strength Threadlocker for large bolts) was used (European equivalent product would be Loctite 270), and with a very simple adjustment, a safe working environment was created.

So in this case, the positive outcome is not measured in saved time or money, but something much more valuable – saved human lives and health.

If you want to learn more about the role that threadlocking plays in proactive maintenance, keep an eye out for one of our webinars.

Or, if you would like to sample Loctite 243 you can now request one from your local Loctite team (select your country at the top navigation on the website).



Why is Loctite Threadlocker better than Nylon insert


Unlike a spring washer, a nylon insert does achieve a very close contact with the bolt surface, closing the gap between threads closer than any other mechanical locking device. However, on-torque is required for this and, due to creeping, the gap develops over time, nevertheless.

Additionally, Nylon insert does not in any way contribute to the clamp load, which is the main requirement the threaded assemblies need to ensure (insert link to first article: Mechanics of a threaded fastener & factors that affect its reliability). In very simple words, it merely keeps the nut on the bolt.

Since quite a high force is required to efficiently tighten the nylon insert, galling can very easily occur during tightening, which also complicates the disassembly.

The same issue of expensive, large inventory of different nylon inserts’ sizes that needs to be kept remains, as it does for spring washers.

Liquid Threadlockers from Loctite actually address and resolve all of the mentioned issues, have a look:


How to select the right Loctite Threadlocker


Using a liquid Loctite Threadlocker on your threaded assemblies will certainly increase their reliability and can secure them against vibration practically forever. Naturally, that may not always be what you want, so it’s important to understand the differences between grades and possibilities they offer.

The first thing you need to do is answer 3 main questions:

  • What’s your fastener size?
  • Which is the required strength?
  • How frequently does the machine / device need to be serviced?

Typically, on smaller size fasteners, lower strength grades like Loctite 222 will work well enough regardless of what kind of vibrational loads they may be subjected to. Also, if you have a high servicing frequency requirement, you’ll want to use a lower strength grade as well.

For assemblies that get dismantled for servicing less frequently (and for bolts larger than M6) a medium strength product Loctite 243 is recommended. Loctite 243 is also oil tolerant and has a higher temperature resistance than Loctite 222 (1800C vs. 1500C).

For threaded assemblies that get disassembled very rarely, the recommended product would be Loctite 270.

It’s also possible to secure a threaded assembly that has already been assembled. For this you can use Loctite 290 which is a product with wicking properties and will creep into the assembly and between the already torqued threads.

Loctite threadlockers pick n mix

There can be a few more factors to consider so it’s definitely recommended you look into our recommendation online or contact our technical customer service if you have any concerns.

Why is Loctite Threadlocker better than a spring washer


Spring washers are one of the most common mechanical devices, used to secure threaded fasteners against self-loosening. The way a spring washer works is that it increases the preload by increasing the contact area, compared to the bolt with no locking device used at all. This will slightly improve the number of cycles it will take for the bolt to loosen, but it will not permanently prevent it. The main reason is that the spring washer doesn’t solve the issue of the gap, free space remaining between the threads of the nut and the bolt. Incredibly enough, there is only about 15% efficient metal to metal contact between the threads. Everything else is empty space that enables plenty of side to side movement for the bolt, which is the main reason for its eventual loosening. On top, being metal itself, a spring washer can cause damage to contact faces and can corrode in place.

Now, when instead of a spring washer you use a few drops of Loctite 243 (or any other Loctite grade that fits the bill – you can find more information on selecting the right product here), the liquid threadlocker completely fills all gaps between threads and prevents any movement of the bolt within the nut. Secured that way, it will be completely vibration proof and stay in place forever – if that’s what you want. If not, the assembly can be easily dismantled with hand tools, for repairs, regular maintenance, any other reason. Although, you will notice that the assembly opens at roughly 25% more torque than tightening torque. Additionally, liquid threadlocker will seal the threads from humidity penetration and in that way prevent corrosion.

One bottle of 50 ml will suffice for about 850 pcs of M10 bolts. And the good news is, whatever the size of your bolts, you don’t need to keep a different Loctite threadlocker on stock for it, as you would have to do with different sizes of spring washers.

Washers vs 243 on scale

Spring washers are not the only mechanical locking solution for the threaded assemblies. There are others, and most of them equally inefficient, but I’ll go into that in some of the following articles.

568 hours of saved unplanned downtime by a tire manufacturer


Whether they manufacture food, medicines or heavy machinery, maintenance incidents are something that all industries have in common, and something they all want to avoid or at least minimise. Whenever a failure happens outside of the scheduled maintenance window, it isn’t only inconvenient on multiple levels because it disrupts the production, it causes actual financial losses. Sometimes the loss is in damages caused by the failure, and sometimes in the loss of productive time, but both have an easy to calculate financial impact.

Tire manufacturer

To give an example, a major Asian tire manufacturer used to experience 284 maintenance incidents per year, each resulting in average of 2 hours of downtime. It caused 500.000 USD in production losses each year!

And the cause behind the failures was, what most might call – trivial: nuts coming loose close to the tire moulding press.

The nuts kept loosening due to thermal expansion of the material during the machine’s service. Initially, the maintenance team just kept re-torqueing the nuts to correct clamp load but naturally, since they were not secured with anything at all, the incidents just kept repeating.

And the solution was as simple as the cause of the problem was trivial. A few drops of medium strength Threadlocker Loctite 243 on each fastener before torquing it onto the bolt and there were no more incidents occurring.

568 hours of downtime became 568 hours of extra production, resulting in half a million dollars worth of extra output.

If you want to learn more about the role that threadlocking plays in proactive maintenance, keep an eye out for one of our webinars.

Or, if you would like to sample Loctite 243 you can now request one from your local Loctite team (select your country at the top navigation on the website).

Solving maintenance challenges with Loctite Threadlockers


Many of the most common maintenance issues in industry can be traced back to failures of threaded assemblies. There is most probably not a single piece of industrial machinery out there that doesn’t have something secured on it by screws or bolts, and those can fail in a few ways as I’ve already described in the previous articles. Two most common problems from maintenance perspective are vibrational loosening and corrosion and seizure. And both have the same root cause: unfilled gap between the threads which allows for side to side movement under vibrations and humidity penetration within the assembly.

When that happens outside of the maintenance cycle on industrial machinery, it means several things:

  • Stopping the entire manufacturing process & troubleshooting for failure
  • Most likely scrapping the batch of whatever items were being produced at the time
  • Disrupting other, related processes in manufacturing

All this means waste of time and ultimately money, which is why zero unplanned downtime hours is the holy Grail of every chief of maintenance everywhere.

And none of them want to compromise this goal by something as mundane and silly as a loose screw. And locking them by Loctite Threadlockers is countless times more reliable than using mechanical fastening devices, simply because the liquid threadlocker is the only solution that fills the gaps between threads and removes the root cause to the two main issues in maintenance.

And gap filling by Loctite anaerobics extends to more than just Threadlocking, all of it useful in proactive maintenance. Have a look:

If you would like to sample Loctite 243 you can now request one from your local Loctite team (select your country at the top navigation on the website).

Or if you’re not ready to sample yet, keep an eye on our webinars calendar and join us in one that suits your needs most to find out more about liquid threadlockers first.

Benefits of Loctite Threadlockers


There are several different methods to address – and try to prevent – the issue of vibrational self-loosening of bolts.

Most of them include the use of additional mechanical devices, to lock the threaded assembly and maintain the desired clamp load.

Double nut increases contact through more thread interface.

Spring washer increases bolt tension through spring action.

Nylon insert creates interference between bolt threads and the nylon insert.

Toothed flanged bolt digs into the surface to provide interference fit.

However, none of these methods tackle the gap existing between the threads of the bolt and the threads of the nut. The gap appears tiny to the naked eye, but it’s still large enough to allow side to side movement of the bolt within the nut caused by operational vibrations. This movement will eventually cause the bolt to loosen, regardless of the mechanical device used to lock it.

gap between threads

The only way to address the issue of gap is to use a liquid Threadlocker which completely fills the gap between the threads, solidifies into a tough thermoset plastic between the two metal surfaces in the absence of air, and in that way prevents any side to side movement. While bolts secured with mechanical fasteners will gradually lose the clamp load after only a few cycles and much before they loosen completely, the bolts secured by Loctite Threadlockers maintain the clamp load throughout (Junkers vibration test).

Washers vs 243 on scale

Apart from being the only efficient way to lock your threaded assemblies (as permanently as you choose to), Loctite Threadlockers also prevent corrosion and galling, increase reliability of your machines, prevent unplanned downtime, increase service life of your end product (in case you’re building them into machinery or devices you’re manufacturing) and minimise costs and complexity of your inventory. For illustration, below picture shows the quantity of spring washers needed to secure 850 pcs of M10 bolts, as opposed to a 50 ml bottle of Loctite 243, which does exactly the same thing, only more efficiently.

Would you like to sample Loctite 243? You can request a sample from your local Loctite team (select your country at the top navigation on the website).

Or if you’re not ready to sample yet, keep an eye on our webinars calendar and join us in one that suits your needs most to find out more about liquid threadlockers first.