Preventing threaded joints from becoming loose is a problem that taxes many involved in assembly. A variety of techniques are used to prevent hardware from working itself free including spring washers, tab washers, locking washers, thread sealants, thread locking patches and SEMS: to name just a few. However, Zygology says that one simple and elegant method of ensuring that when something is fastened it stays that way is a thread locking self-clinching nut from PEM
Quick installation of the PEM thread locking self clinching nut is accomplished by placing the locknut into a properly sized mounting hole and applying sufficient squeezing force using a standard press to embed the fastener's clinching profile completely in the metal sheet. Zygology confirms that all clinching is performed on the fastener side of the sheet, allowing the reverse side to remain flush and smooth without protrusions. Self-clinching technology is also claimed to add reliability to the attachment. The locking nuts install permanently in host metal sheets to become integral parts of an assembly and will not loosen or fall out. Further, they never have to be restrained from rotation with a tool, and never have to be handled again either.
Standard bolts (plus a washer if preferred) are all that is required to achieve a permanent joint that will resist loosening by vibration or heat cycling. Torque settings become less critical as compressing spring washers to create a tight joint is not such an issue.
Zygology states that compared with conventional chemical adhesives or affixed patches, locknuts can help save time and money during production by minimising the number of required assembly steps and materials. There are various PEM self-locking solutions to select from, each its own special thread locking characteristics.
The newest version from PEM is its S-RT range of free running and self locking nuts. Most self locking nuts are of the prevailing torque type which creates friction of the bolt on the nut as soon as the threads are engaged, and whilst this works well says Zygology, the prevailing load makes doing these up more difficult. Also, if many are used, it adds significantly to the time taken to wind on and torque up the bolts. Prevailing torque nuts always have a limited number of cycles before performance begins to drop off.
S-RT nuts use a ramp thread technology which allows the bolt to be spun on with no resistance, and only when the bolt is tightened up do the threads lock and become resistant to vibration. S-RT nuts can also be reused multiple times with no significant reduction in performance, making them well suited for regular access applications, especially as they can be Installed into the same hole preparation as regular PEM self clinching nuts.
PEM® SL™ self-clinching steel locknuts integrate a novel TRI-DENT® locking feature to hold mating screws tight over time by providing sufficient torsional resistance to withstand vibration, thermal cycling, and other loads which could loosen the screws in service. These prevailing torque locknuts, which meet 3 cycle locking performance to effectively ‘self-lock’ an assembly for up to 3 lock-unlock cycles without a significant deterioration in performance. They are available from Zygology in M3 to M8 threads and unified sizes and are recommended for use in aluminium or steel panels down to 1.0mm thick.
PEMFLEX® inserts are said by Zygology to be high performance self-locking nuts suitable for a range of exacting and military applications. The threaded part of the fasteners is split into two segments which apply pressure to the mating screw and result in a torque out load which is higher than that used for installation. PEMFLEX® fasteners have a low rear side profile and the hex body offers excellent pull through resistance. They are available from Zygology in aluminium, steel and stainless steel variants in M2.5 to M5 threads plus unified threads, with thread locking that meets or exceeds NASM25027 specifications.
PEM LAS, LAC and LA4 inserts offer floating threads which allow for panel misalignment to be catered for. The threads on LA inserts are slightly elliptical which puts a squeeze on the mating thread providing a locking feature. Inserts are available from Zygology in steel and 300 or 400 grade stainless steel with thread sizes M3 to M6 (plus unified threads). Thread locking is said to meet or exceeds NASM25027 specifications and non locking variants are also available if required.
PEMHEX® inserts employ a nylon insert to resist threads becoming loose. The insert body offers a low profile and diameter, with its design making it especially suited to close to edge applications. The nylon insert makes the thread well suited to applications where the screw will have to be used and re-used multiple times. PEMHEX® inserts are available in steel and stainless steel with M3 to M5 threads (plus unified threads). Thread locking is again said to meet or exceed NASM25027 specifications.
Zygology can provide samples as well as more information or a demonstration on request. Click here to discover more.