<HTML>Never, never use WD-40 or any other oil based product on strings, action centers, or for that matter any part of the piano!! It works good at first, but over the years it will attract dust, and you will have a sticky mess that will be far worse than the original problem. 30 years ago,  I worked with a technician that sprayed WD-40 over all the pressure points, all of the center and front rail pins, and all of the action flanges on old uprights, thinking that would put things back to normal as far as playing and tuning stability were concerned. At first glance it worked very good, but about 10 years later I was called to tune one of these "treated" pianos, and it was a total disaster. There was so much gummy goo throughout the entire action and on the pressure bars, and under the keys, that it would take an entire rebuilding to correct. Dry dust one can always blow out of a piano, but WD-40 collected dust is there to stay. Just my thoughts, Roy Czekay, Milwaukee, WI</HTML>