First, this is a serious and genuine question, although I accept it may not sound like it.
I'd like to suspend a "swing seat" (reason for quotes might become apparent!) from a joist in the ceiling. I know the joist is strong enough for the load.
However, I want to be able to avoid having the hook/eye bolt in there permanently; in fact I want it to be borderline invisible (in case of family visits; don't want too many questions :) )
I was wondering if there's anything like a hanger bolt, but with the machine thread inside the wood thread. I was then thinking of screwing a removable eye bolt in place, using the "swing seat", and covering the small hole with a plug/cap when the bolt wasn't in place.
Basically I want to reliably and safely suspend a load of say anything up to 200 KG (in extremis), working load 80 KG, which will be subjected to some errr... enthusiastic side-loading, and have it easily removable and near-invisible when not required (i.e. definitely flush with the plasterboard ceiling). I'd also like not to have to knock holes through the ceiling, so was wondering if this could be done with a single drill-hole.
In case a picture really was worth a thousand words, I was wondering if there was something I could get to screw into the joist like my picture below (external wood thread, internal machine thread):