Re: Van Norman #12 Milling Machine

My name is Terry May, I been mostly just keeping quite and learning since I joined the list.
I have been following Dan's discussions about upgrading his RF-45 since this is the machine I have and would also like to convert to CNC.
My question for the group is, have you considered and rejected leaving the Z axis on these types of machines acme thread instead of converting to ballscrew? It seems to a beginner that backlash would not be a problem because of the weight of the head and if better positional accuracy was needed replacing the original acme threaded rod with a precision rod would do the job. I would think that most of the cutting forces would be 90 degrees to the z axis and it doesn't seem like enough force would be generated in that axis to overcome the weight. Perhaps if you were making a sloping cut this would not be true. Am I missing something obvious to those with more experience?
The advantage to this approach is that it would remove the requirement to provide power off protection or counterbalancing.
Thanks in advance for considering my questions.
Terry May