If he's been through a machinist program, it's likely he already has a pretty complete beginner set. At least at the college here, they have a list of tools that are required in order to take the class, and it's pretty exhaustive. They're also patriots I suppose, as you are not allowed to bring certain imported instruments for the class, as I recall. I think it has to be Starrett, or "approved by the instructor" prior. That's a little OT maybe.
Anyhow, unless he asks for something specific, or he mentions something in passing, your best best would be gift certificates to places he can buy the stuff he needs. Cause he probably won't know either, until he needs it. At least that seems to be my experience. But I'm not a professional machinist, so there's that to consider.