SQUARING A STUBBORN X2 HEAD

Resurrecting this old thread as I found it EXTREMELY helpful as I am working on spindle/column alignment.
I have added the screw jacks to adjust X and those work great.
What I am having an issue with is the Y axis and shims.
I started off with the Y kicked out toward user by a good bit, around 0.008". So I added about a 0.003" shim at the top between head and head carrier. This reduced the nod in the Y direction to about 0.003" toward user. So I added another smaller shim. I thought if I over did it, it would nod away from user.
Well, it somehow defied logic and is kicked out even worse toward user at 0.010"!
Of course this whole time X value improved down to 0.00025"!

Any thoughts on tackling this Y nod issue?

Unfortunately, I dont see an easy way to do adjustments without shims. Fabricating jacks for the Y value would be tough because it would have to be on center and the motor is in the way for that.
 
There is no logical explanation for me other than some sort of twist either of the head or the head carrier. So when you tight the head with the shims it twists the head-carrier combination.
Can you check flatness of head or carrier on a surface plate (or using a piece of glass)?
 
I'm not sure what the deal was. I was able to tackle it again over lunch. I think part of it was the order I tightened the head to the head carrier. So I unbolted and tightened again starting with top bolts to seat the shims first. This brought it back to the expected range. I ended up having to shim a few more.

I ended up with the following:
over 4.5" of Z travel I am now at 0.0015" of Y nod and 0.0005" of X nod.

I don't think I can get much better than that with this mill. I'll assemble it all together and tram the table. If things look good, I'll leave it. If not, I am now a damn near pro at tearing this head apart to add another shim. Ha
 
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