Loctite 243 vs Loctite 271: When to Use Each

If you have browsed Loctite products in the past then there’s something that jumps out at first sight, and that’s the sheer amount of numbers and variants out there. Understanding the difference between each threadlocker can be confusing at first, but once you get the basics down it becomes second nature. So today with that in mind we’ll take a look at two of the most popular Loctite products out there: The Loctite 243 vs 271.

The simple answer is that the difference lies fully on the strength of each threadlocker. Loctite 243 is what is called a medium strength threadlocker, while Loctite 271 is a high strength threadlocker. What this largely means is how well they handle heat and how hard it is to remove a coated piece once applied. The 243 is not as resistant to heat, but thanks to that dealing with the pieces is easier. On the other hand the 271 is designed to resist up to 300 degrees Fahrenheit, and due to that fact, trying to remove the coating will be considerably harder. That’s the general gist of it.

Loctite 243 Summarized

As a medium strength threadlocker, the key features of Loctite 243 are its ease of removal and its lower resistance to heat. While that might sound like a huge contention point at first, it’s far from that. The strength ultimately indicates what kind of pieces and surfaces you want to use it on, as we’ll look at in detail further below. In short, medium strength is still a fairly decent strength. And for any fixtures with constant vibration but moderate temperatures the 243 will function as well as a higher end threadlocker, so it’ll be a rock. I wrote about how the 243 compares favorably to Loctite 242 right here actually.

Cure time is rather standard across all Loctite products and the 243 is no exception. The fixture time for the Loctite 243 is only 10 minutes at a steel temperature of 25 degrees Celsius (77 Fahrenheit), but full cure time is the Loctite standard of 24 hours. Permanence is a harder topic to discuss as it’ll vary a lot based on the intensity of the movement and heat of the pieces it was applied to. The 243 is after all designed to be removable so while it should last years ideally you should disassemble and reapply if you detect any movement.

Lastly something that is unique about the 243 compared to other Loctite medium threadlockers is how it handles oil. The 243 is rather resistant to oil and other contamination elements. This means it can largely be applied without needing to do a complete scrub, in fact this is one of its core features. Loctite 243 is conveniently located on Amazon here.

Loctite 271 Summarized

As we mentioned before, the Loctite 271 is a high strength threadlocker which means it is overall more resilient than the 243; that said the 271 is not the strongest threadlocker in the Loctite range and this is important to take into account as well. The 271 is as strong as it gets when it comes to movement, and as such it can only be affected by heat. Anything coated with Loctite 271 won’t budge an inch as long as it’s within it’s temperature range, which reaches up to 300 Fahrenheit.

This largely means two things when it comes to permanence and strength, and that’s largely that if used properly, nothing will move it and it shouldn’t need any further coats. In fact, Loctite 271 is so strong that the only way to remove pieces coated with it is to use a heat source and tools. If you need to remove a bolt with 271 you’ll need to apply heat above its threshold and use tools while it’s hot. That’s why we said that if used well the 271 should last virtually forever, as it’s really resistant overall as long as it remains in it’s proper range.

The cure time of 271 is once again what you’d expect of Loctite, and is similar to that of Loctite 243. Generally speaking the 271 is best known for being a high strength threadlocker that is not quite at the top of the Loctite product ladder. What we mean by that is that others can resist up to 600 Fahrenheit and since these threadlockers can only be removed with heat, such a high temperature range can be troublesome.

In short, strong but not completely invincible is how one should define Loctite 271.

Which is the right threadlocker for each situation?

The core difference between both threadlockers is ultimately their heat range and just how strong they are once properly bonded. So in many senses you can see the 243 as a general use threadlocker and the 271 the kind you should save for really hot areas. Now you could theoretically use the 271 for everything, but as we saw before high strength threadlockers are hard to remove, and some bolts and surfaces where you’d use it might not resist the heat needed to remove it. So in that sense the 271 might prove to be more permanent than you intended.

With that general outlook out of the way let’s take a look at specific examples of when to rely on each threadlocker. Loctite 243 is usually used for any general anti-corrosion and anti-vibration needs for 1/4″ and 3/4″ bolts. It’s largely meant for general use so it can be used for any metal construction in your household, general bolt usage, and pipes that don’t reach high temperatures. You can also use it for certain parts of your car as well, but mostly external pieces that don’t really heat up from use.

On the other hand the 271 is ready to take some heat so it can take on some warmer pipes and constructions that are meant to be exposed to the sun constantly. On your car the 271 can easily take on wheel studs, shock absorbers and press fits. So basically most things not directly dealing with the engine heat, you might want something more heavy duty at that point.

Rely on medium threadlockers for general use and only upgrade to high ones for heat intensive areas. That’s the general gist of it even beyond specifically the Loctite 243 vs 271 comparison. And if you are interested in knowing more about the general range of Loctite products beyond the two we discussed today you can find a summary of them right here.