http://www.quiltingboard.com/t-45983-1.htm Billy has good info - I would read as much info as you can before starting to clean up the machine. It is probably caused by dried up oil or 3 in one oil or some rust. You can fix it up if you can follow directions. There might be more info - look in the vintage sewing machine shop -
http://www.quiltingboard.com/virtual...jsp?vsnum=1013