Thx for all the replys guys .
I'll do as suggested .
Set it up , get it close , take a measurement ....
BTW I know I'm splitting hairs ,or even 1/4 or 1/8 of a hair
And indeed 1mm/2015 or 1mm/2016 ....
I'm waiting on some parts , and I'll do some test as soon as I get movement .
For now it's all theoretical , hence my question .
Pat