I was thinkking that pressing the ring should make it tighter, not loose. Maybe I had zeroed it wrong or had dirt, even when I measured it multiple times.
Maybe it is the caliber I use in cold garage and took mitutoyo from warmth of my home into cold world of repetition.
SOOOO...I made another smaller bushing. This time I used hollow bar, turned outside near, then inside to exact and lastly outside to exact. I used the big display garage caliber and cross check with teh mitutoyo. Both were close, but I choose to trust mitutoyo on this one. It was either just a hair tight or "perfect".
Pressed the collar over the bushing and rushed inside to chek.
IT CAME TIGHT, further measurement conformed that it was just annoying 0,03 mm too tight. i was considering of heating it just a little, but it may need to come off near future.
I was rummagin my reamers and I just knew that I did not have a proper 15 mm reamer, but I ahve two adjustable reamers and lucily I had 15 mm adjustable reamer. I adjusted it just snug inside the hole and gave it fast go.
Now it fits.
But diamond ring and the aluminium backinng disc are not exactly in same plane. It does not need much, but it has just a small wobble.
How to true diamond disc?