Replacing Self-Drilling/Digging Screws

One of the consistent "mistakes" in mechanical engineering that just spells sloppy is the use of self-drilling or digging screws for builds that are supposed to be sturdy such as vehicles. Every time a self-drilling/digging screw is removed or put back, more material is displaced (carved out) and the mechanical bond between the two pieces diminishes every time. Obviously, this is a policy that will end in failure at some point in time. Eventually, the screw does not hold and just falls out. Interestingly, to add insult to injury, sometimes a chosen "solution" is to move on to a larger screw, that again will hold for a while, till it displaces sufficient material in order to fall out.

Fortunately, there is a solution that seems fairly easy to implement. The self-drilling / digging screws are replaced with their normal counter-parts. Matching washers are found and then super-glued around the hole that the screws are supposed to go through. This is very messy and can go wrong easily especially if the super-glue is low-quality and runny. To make matching the washer to the hole easy, the washer is screwed onto the screw and then held in place inside the hole till the super-glue dries up. After the super-glue dries up, some dual-epoxy compound is used around the washer in order to permanently fix the washer to the piece that is being worked on.

Most of this is a very messy business; it might happen that some of the super-glue seeps between the washer and the screw and then dries up such that the screw cannot be removed, or a sloppy application of the two-part epoxy blocks the hole, glue can slide onto the screw treads, etc. With some patience, a decent job can be done and the screw should easily slide in and out of the washer.

Note that this modification works perfectly because the washer is not supposed to bear any tensile force at all; the washer should only be there to provide the necessary treads for the screw to not fall out. The "glue" is really only there to hold the washer upright such that the screw can be fit, but it is not expected that the "glue" should provide any bond.

Aside the fact that this solution makes the bond between the pieces durable as well as easy to assemble or disassemble many times, another nice consequence is that vibrations should be reduced to a minimum. For best results, perhaps, the screws could be chosen to have a high-density tread on the shaft.