Greetings, all. Long time lurker, first post.
I've sorted through "The Book" and this forum, have my parts, and have begun my Book Build. Y'all have tons of great tips and modifications here, and my build is definitely gonna be better for all the advice. As a sort of thank you, I thought I'd post pics of a simple jig I made to keep the BRA tap square.
It's a simple block of wood with a metal lip. Once I drilled the pilot holes in the aluminum angle, I lined up one of the pieces as shown, transferred the pilot hole location to the block, then drilled the block with an 11/32" bit on a squared-up drill press. To use, slip the tap into the hole, align it with the hole in the aluminum angle, and clamp the angle to the jig before tapping. I just finished all six BRA's and they all run squarely.