As I understands it and from my experience and reading here, a wood FP requires some sort of inserts i.e. aluminum, PR, ebonite etc. for threading. The threads needed for such a pen are to small and to fine to thread on wood.
I believe Mike Redburn has been successful in threading wood. I made aluminum parts for a wood pen, that was sent to a swap partner. Don't know if it held together though. But, it was when I mailed it.
The reason for inserts besides threading is that with fountain pens there is a tendency for ink to be in the cap. Without a cap, the ink will most likely stain the cap. The problem can exist in the barrel too.
EDIT: Very cool pen Bruce. I don't know how I missed that one.
Exactly Bob. And ink in the cap, or the barrel, means it will stain through the wood and you'll have a cap with a blue and black and maybe red and green stained pattern.