CHAIR TIGHTENING

First, remove anything you can on the chair: Bottoms, braces, and supports. This is for wood chairs only, the upholstery chairs cannot be done unless the soft material is removed. Chairs that are caned, rushed or splint are difficult to glue if the seats are goo and the legs of the chair are held tight.
You will need rubber mallet or arm strength to loosen or separate any fitting that is loose. Try to get the chair legs and the rungs out of their holes, remove the old glue that might remain on them and then you can use any good wood glue and apply it to the joints. I overuse the glue in the holes and then wipe it off later. You must now use wood clamps at each rung or leg to secure them in place. Use small pieces of wood between the clamp jaws and wood surface. Clamps need to be used to ensure proper seating. Rungs, dowels, and legs that are tapered must be pulled back into position ;and clamped. Remember to wipe The excess glue as you proceed. Repeat this process as you draw the clamps tight on each chair leg, rung, or dowel. The chairs that are bare wood, with no finish on them, make sure you have removed all the excess glue by sanding before you start refinishing. I usually let my chairs sit and dry for a minimum of twelve hours before removing the clamps.
If If the loose joints won't come out of their holes for gluing, you have two choices to proceed. (Never use screws to secure the rungs, legs. or dowels.) One: you may drill four small holes around the rung, leg, or dowels at an angle with the hole opening, then force glue into the holes. (Sometimes this is a temporary fox.) Two: There is a product available that expands the wood fibers and if there is any give to the joints, the very thin liquid will penetrate into the opening. This works well in many cases. (The product has thin, medium, and thick consistencies.)
Good luck tightening those chairs and using them again.