I know this wasn't my thread, but I did learn a little last night:
After some thought (and a trip to work), some of the guys were convinced that 1) I didn?t ruin the part, especially since I had only tapped the 1″ shown on the plans (and the rings are like 1 1/2″ long), and 2) it must be the tap quality.
They lent me a really nice tap (as opposed to the $7.99 tap and die set from Harbor Freight.)
I screwed in the nice new tap, and once I got past the first inch, I immediately felt a difference. When I turned 1/2 turn in, the tap felt like it was cutting, instead of just pushing material out of the way. There was significant resistance at the end of the 1/2 turn. Once you start the 1/4 back out, there is some more resistance, then a ?release.? I could tell immediately that the release was the cutting of little chips from the material.
It was like I heard angels. This is what tapping is supposed to feel like.
(The old one was just steady increase in resistance in, then decreasing resistance out.)
Just one more reason why I should have bought the $80 tap and die set, instead of the $8 tap and die set.
Lesson learned.
From the following picture, you should be able to tell that the thread cutters on the left are nice and sharp, and the apex of each blade comes to a point. The one on the right is not sharp, and the apex is kind of rounded.
http://n999za.files.wordpress.com/2011/07/20110713-003-large.jpg
So now, I have about 1″ of slightly loose threads, and 1/2″ of perfect (remember the angels?) threads. I am okay with at least four threads perfectly engaged, and 16 threads mostly engaged. If my airplane blows away, you all get to say "I told you so."
Hope this additional information helps someone.