Yes you can use epoxy glue inside. You can use it anywhere.
Epoxy will do this .
calcium glue
You can use epoxy or super glue to glue stones together.
Epoxy.
An epoxy is best for this.
Epoxy is best for that.
Use a good epoxy .
Any kind of epoxy is best for this
Most people don't like them glued together, however it could be done with epoxy or possibly super glue.
There are no health risks of epoxy glue,unless you ingest it.
Epoxy itself is glue that will hold to metal.
I would use a two part epoxy.