EddyCurrent: thank you for the links to the resources. I appreciate what I wrote was a little naive sounding. At the moment I have the following questions for interview:

What discipline are you stronger in Turning or Milling?
What is the ratio of your knowledge (i.e. 50:50)?
What number of axis have you worked on?
Can you program on machines?
What controls are you familiar with? How long or to what level of expertise?
What machines have you used? How long or to what level of expertise?
What industries have you produced parts/components for?
What parts/components have you produced?
What materials have you machined/manufactured with?
What is the smallest tolerance you have worked to?
How many thous are in an inch?
What CAD packages have you used? How long or to what level of expertise?
What CAM packages have you used? How long or to what level of expertise?
Can you point out the geometric tolerances you recognise on these drawings?
What are the units of the drawing?
If I asked you to manufacture something for me what questions would you ask me?

The last question is probably the most insightful as it tells me if they are a big picture engineer (asking about cost, quantity, time frames) or a small picture engineer (material, tolerances, heat treatments).

What would you add as questions?

Believe me, having interviewed at least 20 people using this format many of them say they've never had a recruiter ask such technical questions. I even take them through a drawing and ask them to point out geometric tolerances and ask them how they would go about making the component. Thus far my questions have been a good indicator as to the quality of the engineer.

I'm very open to feedback :-)