The dining room table was a fixture for centuries. The very name, table, comes from the Latin word for plank. The first dining room tables were huge and could seat an entire household in the Middle Ages. During the Black Plague, the dining room table became smaller. It became more masculine in the 18th century, and continued changing as time progressed. Antique dining room tables are still serviceable. They can be damaged, but fortunately, it can be repaired.
Inspect the fasteners of the table to see if any scares or mails might be missing or loose. Tighten these fasteners and replace any that are missing. If the joints are loose, you can repair them by gluing them, or even replacing any dowels if necessary. A wood glue would work well for this application.
Strip the finish
If the finish of the dining room table is damaged, you can remove it and start again. You may find that underneath the poor finish is a table made of solid oak. Don rubber gloves, and use a chemical stripper to remove any finish that is flaking or damaged. Use a scraper to loosen any finish that might be remaining. Be careful not to scrape too hard for you could risk damaging the wood.
Sand the wood lightly to smooth the surface. Clean any duct that might be resulting. If you are not thorough in clean up, then you could risk leaving a surface to which the finish might not stick, or worse yet, flake off at a later time. Check the surface feels smooth enough to your liking, then you can start the process of adding a new coat of finish. Choose the finish that you would like to use, such as varnish, linseed oil, or some other finish. Apply the finish in a thin coat, covering the surface of the wood as evenly as possible. Let the finish dry and add another coat if you think it is needed. The old wood may require multiple coats. This is something that you can determine as you are working. Your old dining room table will look as good as new. So good, you may decide to repeat the process with old office tables and bedroom chests.