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 Post subject: Re: Thread or cork?
PostPosted: Sun Nov 26, 2017 5:35 pm 
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Could someone explain why sockets cannot support cork and how does thread support a tenon, I wouldn’t like to damage my flute, it has both cork and thread !


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 Post subject: Re: Thread or cork?
PostPosted: Sun Nov 26, 2017 11:39 pm 
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Jon C. wrote:
Thread! Unless the flute was designed for cork, the sockets will not support cork. Thread also helps support the tenon, by binding it. Flutes with lined sockets are fine for using cork tenons...


Could you expand on that Jon? Not sure I understand what you mean.

My flute is an older M&E rosewood; it's corked. I often find myself thinking about taking off the cork and threading it. The flute is fine, but I would like the joints to be tighter.

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 Post subject: Re: Thread or cork?
PostPosted: Mon Nov 27, 2017 8:36 am 
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Thread supports the tenon by keeping it under compression. Wood expands when moist, and contracts when dry. All flute cracks are consequensial to this fact. Breath is moist. So when you blow down a flute, you're moistening the wood it's made of, and expanding it. Wood absorbs moisture fastest via endgrain, so expansion will be most rapid in places where endgrain is exposed, like the tenon.

Unlike the tenon, the endgrain in the socket isn't exposed to your breath, so it won't expand as rapidly, but when a flute is assembled, it encloses the tenon. So when the tenon tries to get fatter but the socket won't oblige, something has to give, and the socket cracks.

Both cork and thread are there to absorb some of that tension. Both expand and contract much more readily than wood, and compress with little or no lasting damage. Thread, however, as Jon points out, has one additional feature that cork lacks: when moist, it may get fatter, but it doesn't get longer. This constriction stops the tenon from absorbing as much moisture, and thus from bursting the socket. Cork lacks that quality.

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 Post subject: Re: Thread or cork?
PostPosted: Mon Nov 27, 2017 12:11 pm 
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s1m0n wrote:
Thread, however, as Jon points out, has one additional feature that cork lacks: when moist, it may get fatter, but it doesn't get longer.

"May" being the operative word, here. Your chances of thread swelling will depend on the material; natural fibers such as cotton or hemp will be more likely to swell than synthetic ones. I hedge my bets even further by using waxed dental floss rather than conventional thread. The floss is more substantial than thread, so it doesn't take as long to apply; the material is synthetic, so that's good for moisture stability; and the wax not only adds to moisture resistance just in case, it also provides self-adhesion and a bit of lubrication to the socket as well. It may not be as pretty as thread, but the audience doesn't see that.

I must also point out that cork does indeed swell from moisture, but its springy properties make up for that. To illustrate (this is not a recommended procedure for obvious reasons, but still): When one of my tenons' corkings had dried out and compressed beyond the ability to naturally bounce back, I would just steam the corking over the teakettle, and it would quickly swell up back to usable dimensions. But it's only an emergency procedure because it's temporary, and if the practice is kept at there's increasing risk to the wood, so after that, it was the floss for me. You can easily add or subtract as needed. But subtracting's harder once the threading has been in use for a while, because everything gets mushed together, and finding the end of the thread can be well nigh impossible. In that case, I just make only so much of a cross-cut in the threading so I can pull away what I need and make the necessary adjustments; sometimes this means the whole shebang, but this hasn't happened often. Usually entire removal has been strictly by intent. In the course of threading, so long as you leave an end sticking out, finding that end will be easy until you've arrived at the place where you can be confident about the result. Another thing to keep in mind is to not have most of the threading's mass at one end or the center of the span; it forms a fulcrum that will cause the socket to rock. Better to have more thread at both ends.

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 Post subject: Re: Thread or cork?
PostPosted: Mon Nov 27, 2017 12:55 pm 
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To prevent thread from absorbing water you can saturate it with beeswax. You can do this beforehand by melting beeswax and soaking the spool of thread in it, or during/after wrapping by melting the wax into the wrapped tenon. I do both. This keeps the thread neatly in place. Be sure to wipe off the excess and add some vaseline to the outer layer to cut down the friction.


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 Post subject: Re: Thread or cork?
PostPosted: Mon Nov 27, 2017 1:10 pm 
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And that works too. :)

I just like the modern convenience of the waxed floss. No muss, no fuss. :)

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 Post subject: Re: Thread or cork?
PostPosted: Wed Nov 29, 2017 2:16 pm 
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paddler wrote:
To prevent thread from absorbing water you can saturate it with beeswax. You can do this beforehand by melting beeswax and soaking the spool of thread in it, or during/after wrapping by melting the wax into the wrapped tenon. I do both. This keeps the thread neatly in place. Be sure to wipe off the excess and add some vaseline to the outer layer to cut down the friction.


I use a dab of cork grease on the threads when they look like they're drying out, to reduce the wear from friction and (maybe) provide a tighter seal against any air leaks. Cork grease is probably similar enough to beeswax, and easy to apply at room temperature. I've done that for the last couple of years and haven't noticed any ill effects.


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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 1:51 am 
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Interesting that Gromit alerted this discussion to the work I had done years back proving quite conclusively that thread presents a clear danger to flute tenons, but to very little effect. Indeed, the thread celebrates entirely the wrong answer based on really unscientific thinking and total lack of evidence! Is this the Post-truth era as it relates to flute?

Feel free to re-read my study and debunk its findings! http://www.mcgee-flutes.com/effects_of_ ... apping.htm


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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 11:55 am 
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All this bickering over thread and cork, Laurent eliminated both!

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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 12:05 pm 
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Adrian W. wrote:
Jon C. wrote:
Thread! Unless the flute was designed for cork, the sockets will not support cork. Thread also helps support the tenon, by binding it. Flutes with lined sockets are fine for using cork tenons...


Could you expand on that Jon? Not sure I understand what you mean.

My flute is an older M&E rosewood; it's corked. I often find myself thinking about taking off the cork and threading it. The flute is fine, but I would like the joints to be tighter.


Antique flutes were designed mostly for thread, the tenon was unsupported, the sockets were auite thin, by using thread it supports the tenon, the same way bamboo flutes are supported by a thread wrap, also you can minutely control the thickness of the wrap so as not to put tension on the socket, from changing wood saturations.
Flutes that were designed for cork, most mid century French flutes, had silver rings to support the tenon and lined sockets to support for the extra pressure.
Terry’s point of warpage due to overtight thread is justified, but these were flutes over 100 years old, some never being rethreaded. Expansion of the wood and the tension of the thread could warp the thin tenon.
This is easily remedied by not applying the thread as tight, I like to start by using shelac to secure it to the tenon trough.

So if you use cork, make sure the tenon and socket is designed to support it!

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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 12:22 pm 
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These scientific wrangles...when will they end?
Merry Christmas, everybody!


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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 1:13 pm 
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Jon C. wrote:
All this bickering over thread and cork, Laurent eliminated both!

Image

So he essentially said, "Aw, screw it."

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 Post subject: Re: Thread or cork?
PostPosted: Mon Dec 25, 2017 10:43 pm 
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Nanohedron wrote:
Jon C. wrote:
All this bickering over thread and cork, Laurent eliminated both!

Image

So he essentially said, "Aw, screw it."

Pretty much, I guess they were discussing it back in 1820 also! :D

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 Post subject: Re: Thread or cork?
PostPosted: Tue Dec 26, 2017 12:17 am 
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Jon C. wrote:
Adrian W. wrote:
Jon C. wrote:
Thread! Unless the flute was designed for cork, the sockets will not support cork. Thread also helps support the tenon, by binding it. Flutes with lined sockets are fine for using cork tenons...


Could you expand on that Jon? Not sure I understand what you mean.

My flute is an older M&E rosewood; it's corked. I often find myself thinking about taking off the cork and threading it. The flute is fine, but I would like the joints to be tighter.


Antique flutes were designed mostly for thread, the tenon was unsupported, the sockets were auite thin, by using thread it supports the tenon, the same way bamboo flutes are supported by a thread wrap, also you can minutely control the thickness of the wrap so as not to put tension on the socket, from changing wood saturations.
Flutes that were designed for cork, most mid century French flutes, had silver rings to support the tenon and lined sockets to support for the extra pressure.
Terry’s point of warpage due to overtight thread is justified, but these were flutes over 100 years old, some never being rethreaded. Expansion of the wood and the tension of the thread could warp the thin tenon.
This is easily remedied by not applying the thread as tight, I like to start by using shelac to secure it to the tenon trough.

So if you use cork, make sure the tenon and socket is designed to support it!


Not convinced it's as simple as that, Jon, although there is some room for agreement there.

I have come across a few old flutes that I don't believe should be corked, and have advised their owners when asked to cork them. The usual reason is that both the tenon and the socket walls are very thin, foolishly thin in my view. I can only imagine that the flute maker was aiming for a very streamlined look and feel. Consequently, if you tried to cork it, you'd either need to use very thin cork, which might well tear, or you'd have to bore out the socket and/or deepen the tenon trough, neither of which approaches seems wise if there isn't much meat there already.

But such flutes are fortunately rare. Most old flutes have reasonably thick socket walls and tenons, and corking is perfectly possible, and, on the basis of my strangulation study, therefore desirable.

I don't see any need for "tenon support". The tenon is a point of the flute that is only ever under compression. Wood is immensely strong in compression (think railway ties). And I don't see that putting silver rings on flute tenons would provide any useful support. It can only compress the bore. By comparison, the rings on sockets are essential, because the force here is ruptive, and wood is very fissile.

Indeed, it seems to me that tenon rings might well act in a way similar to thread. By preventing the wood expanding when it absorbs water, it's likely to crush the wood fibres in the same way as the bundle of threads crushes them. I say "likely to" because I haven't attempted to study that.

And the socket liners used by the French (and later the English, though mostly on expensive multi-key flutes) are a definite mixed blessing. On the positive side, they look great, and cork runs smoothly and fits snugly in them. But of course they prevent the socket wood from shrinking in dry weather, which can cause splitting in precisely the same way as metal head liners do. Worse, because of the larger diameter and the fact that there is usually thinner timber surrounding them. I've certainly come across plenty that have cracks running from the socket mouth back. Damn hard to get those liners out too!

So, unless someone can debunk the findings of my study, I'm sticking to advocating cork i(where possible). And again arising out of the study, the deeper the tenon trough, the more likely it is that bore compression might become an issue. And, fortunately, the easier it will be to use cork!


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 Post subject: Re: Thread or cork?
PostPosted: Tue Dec 26, 2017 5:52 am 
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I always point out at his stage that if one were to buy a modern bassoon, oboe, clarinet with wooden tenons and pay many thousands of pounds
it will have cork on the tenons.

We "trad" thinkers are way behind in this respect.

H

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