Sometimes a chair will wobble or bump from one leg to another because one (or more) of the legs have worn unevenly. One may be shorter than the others, so the fix seems simple: Shorten the other legs to match. You have to be careful, though, or you’ll wind up taking a little off this one and a little off that one, and then a little off this one, until your chair is suitable for the kids when they want to sit on the floor and eat in front of the TV.
Ask me how I know.
The better way is to measure very carefully. Measure twice or even three times and mark the short leg to avoid confusion. Write down the exact measurements of each leg. The least complicated way to do this is to use four colors of markers or crayons. On the end of the first leg, mark it with the first color, measure, and write the measurement down in that color. Do the second leg with a second color, and so on. When the measurements are completed, you can easily see what needs to be changed.
If there is much of a difference (1/4 inch or more), use a hand saw to take off the extra length, but otherwise, rely on sandpaper. A hand sander will make it easier to get a precise resize done, but you can use an electric sander if you’re very, very careful.
A second reason for a wobbly chair is that the joints are loose. Wooden chairs get loose joints with age because wood dries out and shrinks. To make a joint firm and steady again, remove the piece from the joint completely and clean away any old glue with sandpaper. Sand the inside of the joint, too, making sure both pieces are smooth.
Wipe both pieces with a damp cloth and allow to dry, then apply glue to the leg or rung and push it into the joint, turning it a couple of times to make sure the glue is evenly distributed.
Make sure it’s is in the exact position it needs to be. If you’re gluing a leg into a joint, check the angle against the other legs.
You may need to tape or brace the joint to keep it in place until it dries. Check it now and then to be sure, but don’t move it unless it’s out of place.
Check the glue label to see how long it should take to dry, but give it at least a day to dry completely before using it.
And that’s all there is to it. Your chair should be solid as new.