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Loctite

About the Author:
Kevin "Six" Polk has taught airsmithing for both PTI and Worr Games Products.  Smith is the owner of airsmith.com, an on-line supplier of tools and training materials for airsmiths.

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Loctite - Friend or Foe?
by Kevin "Six" Polk
Photos courtesy the Henkel Loctite Corp.

It is an accepted fact that if you work on paintball markers, even your own marker, eventually you will find a use for a thread-locker.  By far the most popular thread-locker in use today is Loctite®, made by the Henkel Loctite corporation, and will be the focus of this article.  Loctite® is a brand name for a family of adhesive products that include thread-lockers and other adhesive products.  Thread-lockers are compounds that prevent nuts and bolts from becoming unscrewed, either intentionally or through normal use.  They do this by filling in the small spaces between the nut and bolt threads, thereby increasing the contact area to 100%, as we will learn later.  This increase in surface area contact increases the friction thereby increasing the force required to remove the nut or bolt.  Thread-lockers come in a variety of products designed for a wide range of applications; including permanent, removable, and even thread-lockers that work with plastic products.  Unfortunately, most Loctite® users are not aware of the proper procedures, which is what we will cover in this article.  Before we talk about how to use Loctite®, first lets discuss several characteristics of Loctite®.  For our purposes, we’ll discuss several products from the Loctite® family of products commonly used by Airsmiths.

Loctite produces a large variety of thread-lockers, in a variety of colors.  An Airsmith used to be able to tell someone to use blue or red Loctite® and they would use the proper type.  Considering the tremendous variety of Loctite® today, blue or red Loctite® could now mean several different types.  Among the most popular types used by Airsmiths today are 242 (removable strength), 271 (permanent strength), and a new product 243 (somewhere in between).  

Many people ask why Loctite® is so expensive.  According to Loctite®, the primary reason is the bottling method.  As we will learn later in this article, air has a lot to do with the curing process.  The bottles used to store Loctite® have the ability to allow air to move through the bottle.  

Before talking about how Loctite® works, first let’s understand the difference between the curing process and drying.  When Loctite® dries out, it does not achieve the same effect as when it properly cures.  The curing process requires two elements: metal ions and a lack of oxygen (anaerobic environment).  Simply put, when you place Loctite® on a metal bolt and screw it in, you are providing metal ions from the metal, and depriving it of air (oxygen), both elements necessary for the curing process.  This curing (instead of drying) is essential to how Loctite® creates the bond between the threads that gives us the thread-locking effect.

To fully understand how the filling effect of Loctite® creates the thread-locking effect, one must first understand a little bit of thread theory.  If we were to take a cross section of a bolt threaded into a block, it would look like Image 1.  In a perfect world, our threads would look like the Perfect Threads in Image 2.  Unfortunately, most threads are cut using some type of tap or die.  The resulting threads are much less clean, more jagged, as in Image 3.  As a result of these cut threads, the contact of the bolt to the threads decreases dramatically.  Normal cut threads have a contact area of around 60-70%.  Factors such as tap or drill sharpness, heat, cutting fluid, and other factors can affect the contact area of threads.  As a result, cut threads have less contact area, which results in less friction to prevent the bolt from vibrating or working loose.

This is where Loctite® comes in.  As seen in Image 4, Loctite® fills in the small space and, once cured, provides 100% contact with the thread surface area.  This increased contact area dramatically increases the force required to remove the bolt.  Depending on what type of product used, this bond can be removable or permanent.  Loctite® defines removable as being able to be removed with simple hand tools, and permanent as requiring heat to remove.

According to Loctite® engineers, Loctite® currently makes 4 products that are applicable to the Airsmith community: Loctite® products 242 (Removable Strength), a relatively new product 243 (Removable Strength), 271 (Permanent Strength), and 290 (Removable Strength, Wicking Grade).  Although Loctite® does make a pre-applied product, it is considered an OEM product.
 

The 242 product is a light blue color, and being removable strength, it can be disassembled with common hand tools.  The 242 product is by far the most popular product with Airsmiths.  According to Loctite® engineers, the 242 product may require the use of a Loctite® primer agent.  They recommend using the primer product when the threads have some type of coating that would minimize the amount of metal ions, such as anodizing, powder coating, or paint.
 

A new member of the Loctite® family is the 243 product, which is a dark blue or purple color.  Advertised by Loctite® as being more oil tolerant than 242, and “self-priming,” this product will surely gain popularity in the Airsmith community.  The Loctite® engineers tout this product as much more tolerant of dirty threads, especially when oily or lubricated, yet approximately the same strength as 242 which makes it perfectly suited to the Airsmith’s bench.  
 

The 271 product, which is red in color, is permanent, and is the most commonly used in CO2 valve cylinder installation.  According to Loctite®, this product requires the use of heat to effectively break the bond and disassemble the parts, a problem since cylinder manufacturers recommend that cylinders not be heated.  Loctite® further states that the use of excessive force to disassemble can cause thread damage.  
 

The final product recommended by Loctite® engineers is the 290 Wicking Grade product.  The unique property of this product is that it can be applied after the bolt is adjusted.  It’s thin properties allow it to wick down into the space between the threads.  This product can be used after you have adjusted your marker, and want to hold that setting without it vibrating loose.

Proper use of Loctite® involves not only using the correct type, but also applying it in the correct place and using the right amount.  Applying too much or not enough can cause the Loctite® not to have the desired effect.  Proper application involves putting the Loctite® on the end of the threads (Image 5), this assures full coverage over the length of the threads during installation.  Applying Loctite® as in Image 6 would not provide full coverage when threaded as Loctite® would not cover the length of the thread.  Furthermore, none of the previously mentioned Loctite® products are considered adjustable, that is to say that they aren’t designed to be adjusted once the Loctite® has cured.  This readjustment causes a crumbling effect that, while still helping to thread-lock, it reduces the strength and seal Loctite® provides.  For full strength, Loctite® recommends removing the bolt or nut, cleaning off all remnants, and reinstalling per manufacturer’s guidelines.

Finally, a Loctite® coated nut or bolt does not have to be torqued hard to achieve the thread-locking effect.  Loctite® can begin to cure within a couple of hours, but depending on temperature and humidity, can take up to 24 hours to fully cure and achieve maximum bond.  Personal experience has shown that it is important to shake the bottle prior to use.  If the bottle sits for a period of time, the ingredients can settle to the bottom, and unless the bottle is shaken prior to use, it can result in an improper bond.  

One more use of Loctite® is that it can be used in place of Teflon® tape.  Since Loctite® seals the spaces between threads, it also seals air and CO2 pressure as well, and serves to provide an air-tight seal on pressure hose fittings.  If this is done, any adjustment can break the seal.  It is therefore important to remove, clean, and reinstall the Loctite® per manufacturers guidelines to keep the seal.  Loctite® can also help repair the seal with damaged threads, a feat Teflon® tape cannot do.  Finally, when using Loctite® to seal threads, it’s appearance is much cleaner than having white Teflon tape showing; important on many of today’s high dollar flashy markers.

In short, Loctite® use is not just grabbing a bottle and covering the threads.  All areas of application; proper cleaning, application, and installation are important.  The new Loctite® 243 and Loctite® 290 products continue to gain popularity in paintball and Airsmithing, and serve to give Airsmiths a growing arsenal to choose the exact tool for the job.  

Loctite is a registered trademark of the Henkel Loctite Corporation
Teflon is a registered trademark of the DuPont corporation who's staff attorneys send rude letters to us and our sponsors if we don't remind you of that fact

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