I purchased a drill bushing from McMaster-Carr to ensure the elevator horns were drilled directly in line with the center bearing. The bushing was a couple of thousandths too large to fit in the center bearing, so I spun it in my drill press and used some emery cloth to take it down until it fit. Here is the bushing fit through the bearing and pressed up against the left elevator control horn.
The bushing has a center hole sized for a #40 drill bit. Using a bit of Boelube, I drilled through the bushing to make a pilot hole in the elevator horn.
I stepped up the size of the hole using a couple of intermediate bits and finished with a 1/4″ unibit. After a bit of deburring, here is the finished hole. I then repeated the process for the right elevator control horn.
After reinstalling the elevators, I slipped an AN4-14A both through to check the fit. The holes are in perfect alignment. Various washers will eventually be installed here to take up the intermediate space.
