Well... this is wasted effort, most likely.

If your database gets corrupted, you're very likely to lose BOTH tables.

If you want to back up your data, it's very much preferable to (quite outside
of Access) make a backup copy of your entire MDB file.

If you want to do this anyway, for some reason that I'm not seeing, an Append
query will do the job - you'll need two queries, one for each direction.
However, if a table becomes corrupted, you won't be able to append to it;
you'll need to delete it, compact and repair the database, and then recreate
it before you can append.

            John W. Vinson [MVP]