I have talked about threadlockers and important role they play in engineering in one of my previous posts. At that point I’ve only briefly mentioned the post-application as one of potentially needed options. What exactly does post-application mean and what is its purpose? No, it has nothing to do with the post we associate with letters and parcels delivery :-). To post apply a threadlocker simply means that you apply it on a threaded fastener that’s already been assembled in place.
Reasons for this can vary. It may be a part of a larger assembly which you are building into a machine or a device. Disassembling the bolts means losing valuable time. Not securing them, on the other hand, may mean operational downtime later on.
Or perhaps you need to do maintenance activities on machine parts which are too complicated, too hard or too dangerous to disassemble completely.
Or maybe, just maybe you had forgotten to secure it prior to assembly…?
Either way, there is a solution. The name of the product is Loctite 290. It’s an anaerobic compound, with all the properties I’ve described previously, but it has an additional, crucial feature: it spontaneously penetrates between two tightly fitting surfaces, using capillary effect. This allows you to apply the adhesive outside of a thread and it will spread between the nut and bolt. It also tolerates minor contaminations like industrial oils, corrosion prevention oils and cutting fluids, which may not be entirely removable from the application area without dismantling the piece.
This product can also come useful for filling porosities in welds, castings and powdered metal parts.
To see exactly how it works, have a look at the videos linked below.