Hi, Guys. I didn't have time to pick up Break Free or Automatic Transmission Fluid over the weekend, but picked those items up over my lunch break today. However, based on your advice, I was inspired to try my own experiment over the weekend. Sunday afternoon, I thinned some Kroil about 50/50 with acetone, and used a small, round artist's paintbrush to fill the threaded shaft with this mixture. I taped over the hole to minimize evaporation of the acetone. Then I painted this mixture on liberally all around the base of the guard strap screw. I let everything soak for 24 hours. Late today, just before mixing up a batch of ATF and acetone, I decided to give it another try. I couldn't figure out how to safely tap anything without marring the delicate edge of the guard strap. So I improvised two clamping cauls: A round one for the inside of the guard, made from a piece of large dowel, and a flat one for the outside. I gently clamped these cauls in a vise grip pliers and then gently applied some counter-clockwise torque. On the second try, the whole thing let go very suddenly, and scared the heck out of me. I quickly confirmed that I had NOT sheared off the guard screw, and everything was okay. Believe me, I offered some quick prayers of thanks over that happy outcome! Anyway, there is no evidence of rust in the screw threads or shaft threads. It looks like hardened old grease to me. I can't be sure if that was the problem, or if the base of the strap was still painted shut with shellac, but it doesn't matter. I think perhaps the addition of the acetone helped. So I didn't get a chance to try the home brewed penetrating mixture you guys recommended nor any Break Free. But I am pretty sure the addition of acetone to the Kroil did something that just wasn't happening previously.
I do want to thank you guys for your suggestions and encouragement. After this assembly is cleaned up, I can move on to the stock inlets. Those don't worry me too much. As a guitar builder, I am very familiar with cleaning up wood messes--including French polish.
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