FIX SOME FURNITURE YOURSELF; LEAVE REST TO PROS.

Byline: Edward R. Lipinski The New York Times

Time can take its toll on furniture, and even well-made pieces need maintenance and repair occasionally.

The average do-it-yourselfer can easily tackle the simple repairs. More complex tasks - fashioning intricate parts, veneering or reupholstering - usually require professional help. Repairs to valuable heirlooms or prized antiques should be left to professionals.

Before trying to perform repairs, examine the piece thoroughly. Look for structural damage like wood rot, worm holes, broken pieces or loose joints before trying to correct dents and scratches and other surface defects.

Wood rot is not a common furniture problem. But it is often present in pieces that have been stored in damp basements, garages or barns. Probe the wood with a large needle or ice pick to find out the extent of damage. Small areas can be treated by applying a consolidant and filler. The filler, which replaces the decayed wood, will be invisible if painted, but obvious when finished with varnish or shellac. Chair legs with extensive damage should be replaced.

Woodworm is a parasitic insect that eats into furniture. The obvious signs are small holes on the surface and fine sawdust on the floor. In treating woodworm you have to kill the parasite and evaluate the damage. You can usually kill the worm by injecting insecticide in the holes with an eyedropper or oiling can. Let the insecticide dry for about a week. Fill the holes with wood filler. Not everyone agrees on filling worm holes. Some restorers say the holes lend an aura of antiquity.

Broken pieces can sometimes be glued back together. Sometimes it is best to fashion a new item. That may be a job for a professional.

After checking that the wood is sound, check for loose joints. Joints loosen when the wood ages and shrinks or when the glue dries out. First separate the pieces. Then scrape the old glue to expose the bare wood. Do not try to secure loose joints with nails, screws or metal angles or plates. Metal fasteners are not as strong as a glue joint, and makeshift repairs can frequently wreak additional damage.

It is possible that only one joint is loose, but often all the joints will need to be reglued. In that case disassemble the entire piece. First study the construction. Mark all the joints with a wax crayon or a felt-tipped marker on masking tape to guide the reassembly.

The best way to separate the joints is by gently tapping with a rubber mallet. You can improvise by generously wrapping a hammer with rags. If an individual joint is loose but will not yield to the mallet, the old glue can sometimes be softened by injecting a few drops of hot water in the joint seam. When dismantling the item, lay out all the parts systematically for reassembly.

After the parts are separated, they are ready to be cleaned. Use medium-grit sandpaper or a sharp knife to scrape away dirt and all traces of the old glue. Be careful not to remove any wood.

When the pieces are cleaned, try reassembling the individual joints without glue to check how they fit. Some joints may be loose. You cannot depend on the glue alone to hold them in place. You can apply glue to thin strips of wood veneer, which is sold as edging material, and insert them in the gaps.

Traditionally cabinetmakers used hide glue, which has to be mixed with water and heated in a double boiler. Many cabinetmakers now use aliphatic resin, commonly known as carpenter's glue. Whichever glue, the room temperature should be at least 65 degrees.

It is not enough to spread the glue and push the pieces together. You must also apply clamping pressure. Be sure to place a wood block between the clamp jaws and the furniture. Also, insert a piece of wax paper under the block to keep it from sticking, should any glue ooze out. While assembling, check the right angles with a square.

Wait at least 24 hours before removing the clamps. If the finish is in reasonably good condition, you may only have to contend with dents and scratches. Dents can sometimes be raised by placing a moist cloth over the dent and heating it with a hot iron. That generates steam that swells the wood fibers and raises the dent. That will only work if the steam can penetrate through the finish to the wood below. If not, you may have to remove the finish.

Shallow scratches can be treated with touch-up sticks.