Success! Only took 5 tweaks of the cutter position to achieve hole size Nirvana. It has that nice rough scrapie sound as the bearing easily pushes through the hole with the drill quill. Such as easy test. Drill through, slap the 62mm bearing on the bottom, and push it through the hole to see how it fits. You know immediately if its the right size or not.
Since I was starting with a 57ish mm hole drilled with my 2.25" Forstner bit, I couldn't use my 56mm bearing as the pilot. I got a chance to use my fancy new rotating center finder thingy, or Coax if you want to picky.... Dang that worked slick. Got the needle to quiver inside of 1 division on the dial indicator, then swapped to the mandrel, drilled the new 62mm hole.
To test how close to center I was, I initially set the boring bar to just a bit larger than the initial hole I had indicated from, and drilled half way down, leaving a step. I then inspected it visually all the way around to see if the step width stayed consistent to test concentrical-y-ness. I can not tell the difference from one side or the other. Seems just fine to me.
Next thing up is to actually put a 56mm bearing on the mandrel and drill out a test 4 speed housing and see it the hole ends up in the right place.
I also did a thing. To help me check if my holes are the right size, and if the new 62mm hole is in the right place, I figured there was nothing better than using a real C type front bearing housing for comparison. Turns out the C type I took apart has a busted bell housing that was previously patched with epoxy and fiberglass cloth, so there was no way I would ever use it again, so.....
There you go. Now I have a nice easy to handle and measure, C bearing / shift rod plate. Easy to measure the thickness variations, size of the 16mm shift hole (a 5/8 bit is going to be SO close. 0.630 vs 0.625. The rod is very close to 16mm, so a 5/8 hole will need just a tad of honing to make it work. Steve talks about this same problem here http://zhome.com/ZCMnL/tech/240SX5spd/Transmission2.htm
"but later had to ream the hole slightly larger myself with an adjustable reamer because it was too tight"
Dollars to donuts the machinist used a 5/8 bit....
I could pony up and learn about reaming now....
62mm_TestFit.mp4
coax.mp4