I think I can dimple it with a centerpunch, since plainly it's smooshable... I was also thinking of covering the hole on the backside with a loose bubble of duct tape to catch any pieces that might go through. I'm liking the Dremel idea.

Good idea. Another way to catch the metal piece, might be a cut-off piece of pool noodle, especially since neither of bars are there.

Janey - Neat people never make the exciting discoveries I do.

Those pool noodles come in handy for so many things!

I have accidentally broken off that little wire on almost every machine I have owned. I kept on using them. You just have to fiddle with the tension a bit. Finally have a machine that doesn't have the wire!!

What!! The thread goes diagonally to the tensioner directly from the spool? I must admit, I didn't occur to me to even attempt it...

O have trouble picturing this. I have a 66 with the wire thread guide coming through from the back side, located closer to the needle end than the top. It was broken at the "weld" when I got it. We cleaned off and soldered it, and it is fine.

I think yours is the wire guide coming from the faceplate; this is the wire guide coming from the head at the top of the machine, the first threading point from the spool. It's pressed in, not welded.

I mis-read, I meant the very thin wire that is part of the upper thread tension. Never mind...

Victory!! After stepping away from the problem for a couple of months, I decided to try again. I bought a spring-loaded tool called a hammerless center punch with the intention of using it to make a little dimple in the broken-off hook so that I could drill it out without the drill wandering. Well, that little thing produces 3500PSI force, so after making the dimple, I just kept pulling the spring back and letting it fly and the broken piece actually moved backward in the hole until it was sticking a fair way out inside the head. From there, I used a 1/16" hardened centerpunch and hammered at it until it moved the last little bit and finally fell out. Bent the punch, and it took a bit to extricate the punch from the hole (I thought, oh no, this hole is cursed!), but I managed not to enlarge it in the process. The replacement hook tapped in firmly, no problem. I just have to reassemble all the parts I removed and it should finally sew. Thanks for all your input!

Whew what a process. Well done.