If you haven’t been able to find the Plastic Steel epoxy I’ve mentioned for attaching standoffs to panels, there is another brand of apparently similar stuff called JB Weld. A reader of this site sent this link to me. It’s a discussion thread on making inexpensive illuminated pushbuttons, but if you scroll down a bit you’ll see photos of some interesting techniques. He uses flat-head screws instead of standoffs, which is a clever idea. (Personally I’ll stick with threaded standoffs because with screws you’d have to carefully set the height of all of the backing nuts.) I happened to be in a hardware store a couple of days ago that stocks JB Weld products; they appear to be pretty straightforward epoxies with different formulations for speed, materials, etc.
Another Brand of Epoxy for Metal
