Thanks. This sink is a throw-away, but I don't want to have to replace it now. If I damage it a little, that will be OK as long as it still works. I've never had any luck with WD40 in this kind of application. I'll try the penetrating oil and tapping. If that doesn't work, I'll try an oscillating saw under the sink. If that doesn't work, I'll try the saw above the sink.