otlski
Gold Member
After roughening the outside, I would take a small diameter drill, maybe 0.050", and drill through and ascertain the thickness of the plastic. I would then determine what standard tap size would yield a thread pitch that gave me at least three/four turns within that thickness. Note: smaller dia and courser thread is more favorable as long as the three/four turn criteria is met. Run a tap drill through to open it up (do not go over-sized here). Tap the plastic for the determined thread. I would then use a slow cure epoxy to fill the hole, the thread area, and the outside area. Do not use a fast hardening epoxy as they generally are less strong. Be sure to mix the epoxy up in an excessively large batch so as to get the mixing ratio correct. The threads will give some inside "tooth" for the epoxy to adhere to, give shear resistance, as well as providing a longer path out. The longer path is more likely to get sealed at various points along the way. I have used variations of this method before.