newbroom,
Unlike bamboo fly rods where only 3 of the 14,000 plus varieties of bamboo are used I've seen more than a dozen different types used in pipe making. The Danish makers used stainless steel tubing, some went through the bamboo much like the Innertube went through some of Dunhills pipe, although they were removable.
Missouri Meerschaum pipes used them in the past and lately they are becoming available limitedly and they do not use any type of tubing be it stainless or graphite. When the Danish makers used it they went from just behind where it entered the bowl and with room left for the stem to fit into the shank, they sometimes did it so both the stem could be removed from the shank and it might have been a normal tenon or one of stainless tubing, they often made the shank removable from the bowl using the tubing as a tenon as well.
I believe Zack saw this at one of the pipe shows another maker showed him. Bamboo is very resilient and once it has dried I doubt it would collapse because the only soft spot is the actual membrane that separates the leaf nodes, what we call knuckles, the reason tubing is used is it ensures a straight run with a pipe cleaner not getting hung up on the wall of a membrane. Keep in mind not all of the membranes are thin, those that are thick will more than likely pass a pipe cleaner and the thinner ones more apt to have a cleaner roam depending on the distance to the next knuckle.
All of the best bamboo pipes being made today use either stainless steel tubing or graphite tubing, I hope this makes things clearer, warm regards.
banjo
