How Threadlocking Adhesives Enhance Clamp Load Retention – Even in Extreme Conditions

Posted on 12/4/2019 10:00:13 AM By ASC

Threaded assemblies are often compromised by self-loosening and relaxation of tension, particularly in extreme conditions. Mechanical additions like split pins and washers will only prevent the loss of nuts and bolts. Then there are friction devices – but they will only protect against vibration. Ribbon flanged or tooth flanged fasteners do prevent self-loosening, but they are costly and may damage substrates besides requiring bigger surfaces.

Threadlocking adhesives which fill the gaps between mating fasteners and joints, on the other hand, seem to offer the most versatile and effective solution since they protect against leakage, loosening, vibration and corrosion.

In independent tests of Loctite threadlocking adhesives, joins were subjected to vibration and transverse shocks and the clamp load retention curves were recorded and compared to other locking methods. Of these, ribbed flange bolts produced results closest to those achieved with threadlocking adhesives,but it should be noted that these require larger spaces to accommodate the flange, were costlier, and damaged surfaces. Saw-toothed flanges also exhibited good performance, but again, surfaces were unavoidably damaged.

Loctite maintains that its threadlocking adhesives provided a far more cost effective solution and says that the choice of its products for Crossrail boring machines bears out its findings. The bolts that secure components of the boring machines are subjected to extreme pressure, and Loctite 243 was chosen for the task. The company also cites the use of Loctite in extreme off-road racing cars like the Local Motors’ Rally Fighter.

Various threadlocking adhesive formulations are available and are compatible with a variety of metals. When easy disassembly is required, a lower strength formulation can be chosen. These are most often selected for adjustment and calibration screws as well as meters and gauges. Medium strength formulations provide a solution for gearboxes, machine tools, compressors, and pumps. Finally, the higher strength formulations serve applications where a need for regular dismantling is not a factor.

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