Finding a vintage tables and chairs set at a local auction or antiques store --- and for a steal -- can open up exciting possibilities for redecorating your formal dining room. But vintage table and chair suites often come with a downside: the chairs may be rather rickety and worse for wear. You can often restore dining chairs with some simple tools and a little knowledge of furniture restoration.
Diagnose the problem. The most common problem is a loose joint. Lay down on the floor next to a chair. Have an assistant lean on the chair back and sit and move in the chair. Watch for joints that seem to have too much "give." Inspect the four major joints where the legs meet the chair seat frame during this testing. Look at the pieces that cross-brace the legs. Examine the joints where the seat back meets the seat. You should not be able to see any movement at any of these joints.
Move the chair to a workbench. Inspect any loose joints further; discover the reasons a joint has lost its fastness. A mortise-and-tenon joint (formed by fitting a tenon peg inside a mortised cavity) may be out of alignment. A mortise-and-tenon joint may also no longer fight tightly together. One of the spindles or cross-braces may be cracked or broken.
Check the leg joints. Look for wooden blocks or metal angle irons that may connect the legs to the seat frame. Bolts or screws can become loose over time. Try to tighten the nut on a bolt or a wood screw and see if this stabilises the chair.
Replace or repair any broken pieces. Chairs need all their spindles and cross braces. If one of these spindles is broken, gently remove it from the chair. It is nearly impossible to reliably repair a cracked or broken spindle: ask a local woodcraftsman to make a copy of the spindle using a turning lathe. If a spindle has broken off and a tenon peg remains in the mortise hole, grind the peg out of the hole using a drill and a drill bit the size of the hole.
Remove all the old glue if possible using warm vinegar. Apply new glue to all joints. Use woodcraftsman wood glue.
Clamp the furniture. Use several special furniture clamps to force all the joints of the chair into tight alignment. You can often rent these furniture clamps at tool rental stores. Clamp the chair from at least two, and ideally four, directions. If you do not have enough clamps to cover all the joints in the chair, start by clamping the legs and the seat. Move on to legs and cross braces, then seat and back, and finally any back cross bracings. Make these clamps very tight. Let the glue dry overnight.
You can also use tightly drawn ropes or twine to clamp chairs for regluing.
Avoid introducing new screws or nails into vintage chairs in order to repair joints. You will very likely cause the brittle old wood to split and damage the chair even further.