I need to attach a bronze piece to some stainless steel with no back access, the bronze piece has two all-thread rods coming out of the back to insert into matching holes in the stainless. Originally there were nuts to secure in the back but I can no longer access the back panel. Does a toggle bolt or anchor exist where I could just hammer the rods in, as I cannot screw them in?
Given the hole you appear to have backed youself into, "glop some thick epoxy through the holes, slather more on the rods and back of the thing, and depend on adhesives to hold it" appears to be the workable "solution" without cutting access.
A more complex approach that might be more secure would be to drill out the holes larger, at a tap size for a large threaded rod. The rod would be large enough that you could have a machine shop bore a hole through the center a bit bigger than your small threaded rod. They could also weld push nuts onto the far end, but the main advantage would be a much larger area to apply epoxy to for bonding the smaller rods in place.
Or cut an access hole, use normal nuts and lockwashers and threadlocker, then weld the access hole closed if vandals are your issue. If they are harvesting bronze for the scrapyard that may not work, as they can still break the thing with a sledgehammer and haul the broken parts away. The perils public art is subject to...
