Loose chair legs.
Just a post noting my experiences figuring it may help some other lost soul out there searching Google Groups...
Problem: Loose chair legs. Mortise and tenon joints. You know the routine... chair legs loosen, so you scrape out the crusty glue, re-glue and the chair is fine... for a couple months. Soon the legs are all loose again and the chair feels like it's going to implode any day into a pile of kindling.
Solution: POLYURETHANE GLUE. A common brand is Gorilla Glue. The stuff is manna from heaven. Elixir of the gods. Wood glue extraordinaire. It's kinda expensive. Buy it anyway.
For those that have never experienced polyurethane glue, it looks like thick maple syrup and as it cures, it foams a little, filling any gaps and spreading through the joint. I'd say it triples its volume. Just buy some and try it out... it's cool.
In addition to gap filling, the cured glue is VERY tough and I think even a tiny bit flexible. At the very least it's not brittle like some glues.
Anyhow, I glue up the legs, the excess oozes out and once dry, can be scraped off pretty easily. For me, where the legs mortise into the underside of the seat, I just leave the extra glue for a little added strength. No one will see it unless they are slithering around your kitchen floor on their back, in which case, you may have bigger problems than a little visible glue.
I have a few formerly troublesome chairs repaired with polyurethane glue that are still rock solid over two years later. And keep in mind one of those chairs is being used by a teenager that leans back in the chair, leans forward, leans sideways, and oddly finds it comfortable leaning back on ONE rear chair leg. Two plus years and it's still as solid as the day I glued it up.