Machinery Adhesives Frequently Asked Questions
Q1: How do you define anaerobic in relation to your products?
A: Anaerobics, that include many of our threadlockers, pipe sealants, retaining compounds and flange sealants, are products that cure in the absence of air. These are products that are designed for metal-to-metal assemblies although they are sometimes used for other materials as well. The presence of metal (ions) accelerates the cure of these products. When you assemble parts with an anaerobic and you have excess squeeze out, outside the joint, this will not harden due to the anaerobic nature of the product. Simply wipe the excess away with a common solvent like acetone or isopropyl alcohol. Typically anaerobics fully cure in 24 hours at room temperature under normal ambient conditions when properly used.
Q2: If anaerobics cure in the absence of air, how come they don't cure in the sealed bottle?
A: The anaerobic bottles are specially formulated oxygen-permeable polyethylene bottles that allow air to pass through the wall of the bottle to maintain stability of the liquid product inside the container. The bottle is also not filled to the top for stability purposes. A 50 ml bottle does indeed contain 50 ml's of product in a larger bottle.
Q3: I cannot get an assembly apart where a threadlocker was used. What solvent will break the threadlocker down?
A: No solvent will wick into the joint to break the threadlocker down. This is either hand tool removable at room temperature or if not, it requires high temperatures of 450-600°F to separate parts. The products are thermoset plastics in the cured state that soften at higher temperatures. Thus, you need to disassemble while at the higher softening point temperature. Do not let this cool down first. Otherwise, it will resoldify. Solvents like methyl ethyl keytone and methylene chloride can be used for clean-up of residue only after disassembly.
Q4: Can I use a threadlocker for non-threaded assemblies like locking bearings or bushings in housings or on shafts?
A: Yes, you can. Traditionally we recommend retaining compounds like LOCTITE 609 or LOCTITE 603 but threadlockers are the same base chemistry and could be substituted in many cases. In fact, years ago Threadlocker LOCTITE 271 was referenced as Stud & Bearing Mount. Inversely, you could use retaining compounds to lock threads as long as you're cognizant of the fact that most will permanently lock threads.
Q5: What is the optimum fit for using anaerobic retaining compounds if I want to maximize my shear strength?
A: A slip fit would be suggested. The optimum fit for thinner products like LOCTITE 609 & 603 is 0.001-0.003' on the diameter. The optimum fit for thicker products like LOCTITE 620 & 638 is 0.002-0.004' on the diameter.
Q6: Do you recommend using anaerobics on plastics?
A: Anaerobics are generally not used with most plastics. Anaerobics will stress crack some plastics including many thermoplastics like ABS and polycarbonate. If the product is used for metal-to-metal but in close proximity to plastic, there is the possibility of excess liquid product or vapor affecting the plastic. In the case of compatible plastics like acetals, the anaerobics are simply not the best family of products for effectively locking and/or sealing. Often cyanoacrylates are substituted if they meet the other application parameters.
Q7: Can the cure of anaerobics be accelerated via heat?
A: Yes, you can heat cure anaerobics to achieve faster full cure. Typically you can heat cure these products at 250°F (125°C) for about one (1) hour or go as low as 150°F (66°C) for about three (3) hours. The one trade-off is the fact that you will probably reduce your ultimate strength some. Whenever you accelerate the cross-linking of the polymer, you can reduce your ultimate strength. Carefully test for suitability.
Q8: Do I need to use a primer with anaerobics?
A: We recommend the use of primers such as LOCTITE 7649 & 7471 with most anaerobics where both parts are classified as "inactive" metals. These metals lack the presence of iron or copper content and thus, lack the "active" metal ions required to fully cure the product in 24 hours. These metals include plated parts, stainless steel, galvanized steel and anodized aluminum, to name a few. If, on the other hand, both or at least one part is an "active" metal, such as plain steel, brass, bronze, copper or iron, there is no need to use a primer to ensure full cure in what is typically 24 hours at room temperature.
Q9: What is the proper way to apply threadlockers for both thru and blind hole applications?
A: For thru hole applications, such as a nut and bolt combination, threadlocker is applied just to the bolt, coating 3 or 4 threads, going all the way around the diameter, and then assemble. On the other hand, it's critical to apply the threadlocker to both male and female threads for blind hole applications such as a bolt going into a closed housing. If it's applied just to the male threads and torqued down, air pressure will force most of the product back out as you assemble. This will result in incomplete coverage and partial cure only, leading to premature failures.
Q10: Are threadlockers fungus resistant?
A: Our general statement is that threadlockers will support fungus growth that is already present but will not promote growth otherwise. Many threadlockers conform to military specifications and these specifications (Mil-S-22473E, Mil-S-46163A) specify that the polymerized compound will not support the growth of fungus when tested to the requirements of the military specification.
Q11: Are anaerobics compatible with rubber parts the products may come in contact with in the liquid state prior to cure?
A: There are no long term studies for anaerobics and compatibility with various elastomers. There is a general consensus though that liquid anaerobics upon prolonged contact can negatively impact some elastomers in the form of swelling, cracking and weight change. Customers should carefully test products for compatibility. Some Loctite dispensing equipment utilizes Viton o-rings and seals specifically because this has been deemed suitable for use with anaerobics for a reasonable amount of time. Once an anaerobic cures, there is no compatibility concerns between rubber hardware and the cured, very inert plastic film/anaerobic.
Q12: Can anaerobics be used on oil-impregnated parts?
A: Yes. Anaerobics can be used on oil-impregnated parts. Just wipe the part clean prior to applying the product. The more oil tolerant products like LOCTITE 603 & 243 are good choices because they have better cutting oil action and thus, cure properly and bond and seal effectively after cure.
Q13: Can I substitute LOCTITE 518 Gasket Eliminator for LOCTITE 515 Gasket Maker?
A: These are both anaerobic flange sealants designed for rigid machined flanges. They are similar products with one of the key differences being that LOCTITE 518 is a better product for use on aluminium flanges. Thus, LOCTITE 518 probably can replace LOCTITE 515 for most applications. However, LOCTITE 518 is generally a faster setting anaerobic and it may tend to cure too quickly on very active metals like brass. In this instance, LOCTITE 515 may be a better choice.
Q14: How do we define breakaway and prevailing torque?
A: When we apply a threadlocker to a bolt and finger tighten a nut down, we let this sit for 24 hours and allow it to fully cure. We then take a torque wrench and break the bond. The initial reading on the unseated assembly is the breakaway value (remember, this is not torqued to a specified value such as 100 in lbs). This shows us the strength of the threadlocker alone. They then continue turning this and the average of four quarter turns provides us with our prevailing torque value. This shows us how much friction or drag is left to continue turning the nut. If for example, on the other hand, we torque the assembly down to 100 in lbs, and we use a threadlocker with a breakaway of 50 in lbs, the breakloose value initially on this seated assembly is 150 in lbs (100 + 50). The difference between what you torque this down to (100 in lbs) and what you breakloose at, (150 in lbs) is 50 in lbs and this is referred to as torque augmentation. The main function of any threadlocker is to maintain your torque. It's been determined that over time due to various factors such as vibration and side sliding, that you lose up to 30% of your on torque. The goal is to choose a suitable threadlocker that provides a breakaway value equivalent to 30% of what you torque the assembly to in order to maintain your torque over time.
Q15: Are the new LOCTITE stick threadlockers 248 & 268 the same as any of LOCTITE's liquid threadlockers?
A: The stick products are similar but not identical. Their chemistry and function is the same but there are some distinct differences. Stick products are not recommended for blind hole applications. Blind hole applications require applying product to both male and female threads and this would be very difficult to do with the stick formulations. The stick products yield strength values that vary some from their liquid counterparts. See the TDS's for specific data. Also, the stick products are not tested to any military standards like their liquid counterparts.
Q16: The new Worldwide formatted data sheets include a graph for Cure Speed vs Substrate which is often misinterpreted. A similar graph for Cure Speed vs Activator is also misinterpreted for the same reason. What is misconstrued?
A: Many people misread the graphs and assume the products never fully cure for the timeframe specified in the graphs. However, the graphs simply illustrate the percentage of strength achieved for a specified time on different metals in comparison to plain steel. People make the assumption that the products take a very long time to cure when in essence the graph is just portraying lower strengths on these other metals compared to plain steel. The Cure Speed vs Activator graphs also simply show comparative strength with, for example, dichromated steel versus plain steel, for a specified timeframe. Some people interpret this to show that the product doesn't fully cure in the maximum time of 72 hours portrayed in the graph whether activator/primer is used or not.