This project describes how to replace teak deck plugs over fasteners that won't stay in place due to being sanded too thin. If the deck is fastened from above and the surface gets lower over the years, the heads of the fasteners get closer and closer until the teak plugs covering them get too thin to stay in place. See Figure 1.
This article refers to round head screws. The problem is minimized with flat head screws since the teak plug can gain some support from the flush surface at the bottom of the hole and doesn't tend to pop out so easily when stressed off center. However the technique in Figure 3 can be applied to flat head screws if necessary.
It is commonly not practical to remove the old screws, deepen the hole and replace them. By the time a teak deck has worn down this much, the fastener will have deteriorated to the extend that they can rarely be removed. Attempting removal, if you can get enough bite with the screwdriver, usually results in the head twisting off and now you have a problem that is ten times worse.
Figure 2 shows the crossection of a teak plug that has had a cavity for the screw head drilled out of the center so it fits over the fastener. This has two advantages. Not only are you increasing the surface area in contact with the hole but you are providing a solid base for the bottom of the plug to rest on so it won't be dislodged by off-center stress.
Figure 3 shows an extension of this process where the teak surrounding the fastener has been deepened, leaving the fastener in situ on a little island. A longer plug, again with a clearance hole for the fastener and the island now can get more contact with the sides of the hole. To deepen the ring around the fastener, you will need to select a "Forstener" type bit that matches the hole diameter and grind off the center and blade to the required diameter.
Over the years it has been my experience that epoxy and teak on an exposed deck are not a good marriage. The problem is that the teak expands and contracts so much with changing moisture levels that it fractures the epoxy which remains rigid. This process is aggravated somewhat when underway by the stress and flexing of the deck.
It may be that in the small size of a plug that it doesn't matter but as a result my preference has been to use an adhesives that remain flexible when cured.