I am trying to obtain 120vac power from a press powered by 240vac w/no neutral. I am using a transformer to apply 240 to the input for 120vac output. Which of the output legs would be considered the neutral?

Tell us more about the transformer, what are primary and secondary voltages listed?
What is the rated VA?
That will give us a better idea of the type of xfmr we are talking about...
What are using the 120V for?