Well, the first real 62mm hole in a real 4 speed housing has been bored. The bearing fit is a nice tap-in, just like the Stock C type hole, and the location is as perfect as close as I can measure. There is exactly 4mm between the two bores.
One slight issue that may lead me to use the coax indicator instead of the pilot bearing for centering. Maybe. This time, when you first move the bearing up/down into the 56mm hole with the quill and start moving the table X/Y to get the bearing to slide nice and evenly in the hole, there is quite a bit of X/Y motion possible with the bearing still passing through. You have to listen very carefully to get the least drag noise, and to get the minimum quill effort. This is not slop between the bearing and hole, or bearing on the mandrel, this is the table motion deflecting the casting on its plywood base I suppose. It’s pretty easy to get close. I drilled the hole, it worked out fine, BUT there is a clue that I was not perfectly centered.
The bearing stays engaged with the old 56 mm hole until you are about 75% of the way through, then the bearing pops out the bottom, and is no longer supporting the quill location. At that moment, you can see a mark around the circumference of the bore. It’s tiny, I can’t feel it with my fingernail, but I can see it. So the bearing was not dead center to start with. Maybe its just a remnant of the motion induced when the bearing left the bore.
Oh so close.
Measuring the 4mm space between the two bores is tricky. My caliper is too long.
So I set my micrometer to 4mm. You can’t measure that thickness with two curving walls, so it’s resting on top.
I need to make a 4mm gap gauge of some type.
This is a 4mm drill bit. Parallax is a bitch.... picture is not perfect.
This is the 62mm bearing in place.