I have a factory-built Early-American style oak chair (one of six) that
has failed at a glue joint in the middle of the chair bottom. There is
no tearing of wood fiber, just a clean break at the glue line. The
bottom is still held together by the legs and back. The only way I
noticed it was that I happened to feel the crack when I was sitting in
the chair, so that part must not be under much stress. The rest of the
joints are all still good and tight after 18 years of daily use, so I'm
reluctant to disassemble them. Dare I just pry the bad joint apart and
squirt it full of glue? I'd use Gorilla Glue, but it's so messy.
Would Titebond hold without surface preparation? Maybe I could just
slide some sandpaper through the crack work it back and forth?

If you don't want to take the chair apart you might want to look at

http://www.leevalley.com/wood/page.asp?page=30261&category=1%2C110&SID=&ccurrenc y=2