Repairing a wood chair isn't always something a novice can do successfully, but tightening a wood chair arm that has worked its way loose is typically a simple fix. All you need are the right materials, tools, and instructions.
Step 1 - Check and Tighten Loose Joints
Joints that are glued in arm chairs can eventually become loose, making the chair arm unstable and wobbly. If possible, remove loose arm dowels fitting into these joints. Clean out any debris in the joint, sand off the dowel that fits into the joint, apply wood glue to this dowel end and re-insert it into the joint. Allow the glue to set before using the chair.
Step 2 - Insert Screws
In joints you cannot tighten and secure by applying fresh glue, you can tighten by inserting wood crews. Drill a hole for a screw in the chair piece that contains the joint into which a chair dowel should be glued and tightened. Use a counter-sink bit to ream out the hole you've drilled. This will allow the screw head to be inserted far enough into the hole that the screw head will be below the surface. Fill with wood filler and allow it to dry. Sand and apply varnish or paint to finish.