well if ya ever do, please let us know
or have someone shoot a video 
This seems like such a non-issue.
My only problem is something that is so normal, acceptable and seemingly benign is being made out as something dangerous and a thing to avoid.
Look at a thread wrapped tenon and ask yourself, does it have enough energy just sitting there to crush the wood underneath? It seems ridiculous to me to think a thread wrapped tenon is really a coiled up bundle of crushing force. Especially when you’re not putting crushing force into wrapping it in the first place!
As the tenon expands with moisture the thread is going to stretch, unravel and give somewhat. The thread itself will have to expand and contract with moisture stretching and slightly unraveling itself out over time as well. At no point under normal circumstances do I think that a normal thread wrap could achieve enough force to crush a tenon, not even close.
There are plenty of instruments out there that use thread wrapped joints, flutes, bagpipes, bassoons (with large thin tenons). Never heard of it being a problem for them before.
I have seen this a lot in antique flutes. I haven’t had many cork tenon flutes in the shop, so haven’t seen any distortion. Another factor, the tenon is thinned at the thread section, this coupled with the thread and shrinkage at the tenon, would be another factor.
Here is a new angle, I have also seen a lot of tenons, where the thread is loose from the tenon, the tenon has shrunk and the thread has not, this causes the sections to get stuck, which is a lot of fun…
All in all, I think the support that the tenon gets from the wrapped thread, out ways a little distortion in the bore. Anyway it probably improves the tone! 
George, I don’t think there is any question, it’s real and I have two fine examples (Weedies and this current flute) to point to. What else could have strangled these two flutes, causing significant bore compression right in the middle of the tenon trough?
We also have plenty of less dramatic evidence - lots of old flutes I’ve measured have evidence of some bore compression, again, right under the tenon troughs.
I don’t know if thread expands lengthwise significantly when it gets moist, but of course, it shouldn’t really get very moist if it’s been waxed and/or lubricated with cork grease or some equivalent. Unlike the wood, which will get very wet, at least on the inside.
And I’m not saying thread wrapping is the kiss of death. I imagine that the soft yellow stuff pipers use, lightly applied, will probably be fine (although I’ve never done any tests, so don’t assume anything!). This stuff looks to me (under the microscope) to be poly rather than cotton. It’s double-stranded, and each strand is made up of maybe 20 filaments.
The thread is 0.1mm thick, and can support a load of 700gms before snapping. The thread trough is 15mm long, and about 1.3 deep on average, with respect to the inside of the socket. So it would accommodate at least 150 x 13 threads without packing them in, which could support a total weight of 1.365 tonnes. But these were packed in - the threads were drawn very tightly, to the extent that the flute was not easy to assemble - the pack was very hard. I think we’re dealing with the classic immovable object. The swelling of the wood supplies the irresistible force, and something had to give. As usual with flutes, it’s the wood.
Terry
The socket/barrel pressing against the tenon over time is my guess … you said all flutes naturally have some warpage due to humidity as well, is that a place that flutes naturally warp? That tenon is one of the thinnest parts of a flute, right?
You could make a couple of tenons in scrap wood and do a normal thread wrap on one and leave the other bare and see if there’s any difference in compression/warpage over time.
As with most things, the following is true:
Just because you can’t wrap your head around it, doesn’t mean it isn’t happening.
I’m inclined to believe these flute-making fellows. In addition to our two esteemed contributors here, I’ve also had conversations about this very thing with Patrick Olwell, Chris Wilkes, and other makers and restorers of no little repute. To a man, they all acknowledged tenon warpage as a possibility when using thread; each had a preferred type of thread and application technique to avoid damage.
How many such reliable reports from the field would be enough to convince the skeptics?
Rob
hah! I’ve wrapped my head around lots of things that never happened!
But have you wrapped your head with thread? 
Best wishes.
Steve
One thing that might be a factor is that amateurs might add string but they would be less likely to add cork. I could see how years of adding string would cause problems. Of course, Boehm had the most elegant system and used neither.
This is an odd one with lots of variables to it.
I mean just the type of thread alone brings in lots of chances to screw it up. I’m sure the type of cement used to attach the cork and the width and breadth of the cork also play a part in it as well as the type of wood, the lathing of the tenon, the bore of the flute, treatment of the wood, structure of the wood, and so on.
I guess I’m saying with the right set of variables, I think it’s absolutely possible to warp or crack a tenon with either joint material. For example, Using a hard, brittle glue to put cork on a thin tenon might, over time, have the exact same effect as Terry describes.
It’s entirely possible that we see more warping and cracking from thread just because it’s been used for a longer time by more makers then cork and the threads used weren’t always cared for correctly over time or were just unsuited for the job to begin with.
I’m with Jeff (mandoboy) on this one. As an amateur woodworker I’ve seen lots of furniture and boxes that have self-destructed from their own internal forces. (some actually weren’t mine 
)
Course, I would never discount anything Terry or Casey say because they are both unbelievably knowledgeable about these things and I’m just speculating so I think this puts us back to the same cork vs thread argument that’s been raging for years around these parts
I have both threaded and corked flutes and I’m just going to play and if they ever break, I’ll get them fixed.
I believe the main problem with cork is poor application, resulting in an ill-fitting joint. Unlike thread, cork has very little tensile strength and so can’t be pulled taut around a tenon.
Rob
yes, of course!
only in the summer months though.
Fascinating discussion, and what I’ve gotten out of it may be condensed to “Squish Happens”. Thanks for the topic, and I’ll mind my tenons all the better now.
He made wooden flutes too, you know, and I believe (haven’t gone to check) used the “French slide” design which has the metal male head-liner sliding into the metal upper body socket/tenon, the outside of which is corked and slides into the metal lined socket in the head…
I had a feeling you would call me on that. Which of the two are still around?
Can’t get one past Jem! 
Quite a few wooden ones extant - go check the DCM! (Here’s a link preset for a search on “Boehm”:http://memory.loc.gov/cgi-bin/query/d?dcm:0:./temp/~ammem_st1B:.)
Apologies for going back up-thread for this, but …
Not disputing that they would both say that poorly applied thread may cause damage, but Chris at least still prefers thread to cork (at least on some days 
). What does Patrick think?
Paddy uses cork on his own flutes for the most part, but I’ve seen him thread a few tenons on older flutes, either to match what was there or for some other nefarious purpose. I also know a few folks whose Olwells came with thread, by request.
Rob
Thanks Rob. That’s pretty much as I would have guessed.