Dear Jim: As an engineer, I often have the same question as to how far to take the drawings that I produce before handing them off to a timber framer. The answer is "it depends." When I work with a local framer that I have worked with frequently, we sit down at the begining of the project and work out the best structural approach. We each rely on our experience to guide this process. I then size members of the frame, assuming typical joint details that are commonly used by the framer. Where there are extreme demands placed on a particular joint, I will detail it. I hand this set off to the framer and he works up a set of shop drawings based on my plans. I review them and check the joinery that I had not previously detailed.
I have also worked with framing companies far removed that I would most likely never work with again. In these cases, the relationship is not there, so we both must go a little further and incur the cost of a little more give and take in the back and forth design process.
When I am asked to design the structure for a timber frame, I always encourage the architect or owner to find a timber frame company that they are comfortable with that also has a good working relationship with an engineer. It makes for a better project. If they insist that I must be their engineer, then I do the best I can to familiarize myself with the way the framer prefers to do joinery. I then try to accomodate the framer's standard and signature joinery etc. into my design. I hope this helps.
Best regards, Chris Hoppe