Reasons for the failure of threaded assemblies
A threaded fastener can loosen due to vibration and it can result into catastrophic machine failure. Gaps naturally exist between the mating surfaces of threads that directly impact on the fastener’s ability to stay tightly fixed. Tiny though these gaps are, they allow side-to-side movement when exposed to vibration and thermal expansion/contraction. The side-to-side movements loosen the mated parts, reducing clamp load and ultimately causing the mechanical fastener to fail. Mechanical locking devices were invented to prevent the failure of threaded assemblies but they have inherent flaws and the user needs to keep an extensive inventory of expensive parts to fit all the fastener shapes and sizes.
The reliability of anaerobic threadlockers
Anaerobic threadlockers act as lubricants during fastener tightening and allows applied torque to be converted into high clamp load instead of dissipating as friction or heat. Once cured, the threadlockers can provide a reliable seal that would prevent leakages, galling and corrosion that can seize threads and prevent disassembly. Anaerobic threadlockers are single-component adhesives that can cure tough thermoset plastics when exposed to active metals and deprived of air. They can completely fill the void between the interfacing threads and prevent side-to-side movements that usually cause the loosening of the threaded assemblies. Threadlockers ensure that the threaded assembly will stay locked and sealed for the entire length of its service life. This makes the adhesive cost effective and practical for locking devices.
How to apply the liquid threadlockers
- In order to achieve optimum performance, all parts must be cleaned and free from contaminants like oil and grease.
- A dispensing system makes it more convenient to dispense the liquid threadlocker
- Most liquid threadlockers are designed to be applied at the moment when the parts will be assembled but it can also be applied on parts that have been assembled.
- For through-hole assemblies, threadlockers can be applied where the nut and bolt meets when fully tightened.
- For blind-hole assemblies, threadlockers are applied to both the bolt and the mating threads.
- For post assembly, low viscosity, water thin liquid threadlockers can be applied.
In the selection of threadlockers, low strength is ideal for fasteners that are < ¼” (6 mm) while medium strength is designed for ¼” to ¾” fasteners. High strength liquid threadlockers deliver high strength to ¼” and ¾” (6 mm to 22 mm) fasteners.