CRC makes Knock’er Loose which you can purchase at Grainger.com. It has a freezing agent which allows the solvent to penetrate the fastener, fitting or shaft. I have used it successfully many times (sometimes you will have to apply it twice if the item is encrusted with corrosion or mineral build-up).
A lot of others have recommended Knock'er Loose, but I didn't know it had a freezing agent. That could help a lot. I'll stop at Grainger's and get some tomorrow.
Thank you.