Hi:
I had alot of problems with the X axis on a CNC lathe (Not a Haas).The machine would not repeat on X, or drifted as the day progressed. Turns out it had nothing to do with the thermal expansion.It was a stiffness/levelling issue.
Someone will probably argue that the castings are stiff, etc. as I did when we tried to solve the problem.
If you are a skeptic, mount a dial indicator on the crossslide, and indicate on a piece of stock. Have someone turn one of the jack scews near the headstock (+/- 1/2 turn), if you see a change in the indicator, consider fixing the machine to the floor (provided it's concrete).
Here's what we did:
1. Levelled the machine (spirit levels on both axis).Took a long time!
2. Bolted it to the floor.
3. Re-checked the levelling.
Since then (3years ago) it's been able to hold dimensions without a problem.
regards
----------------
Can't Fix Stupid