Just thought I’d whip up a quick thread to see the input provided by some flute folks here on which threading materials (cotton vs. dental floss vs. polyester/silk, etc.) you’ve found to be more efficient than others or that you favor, etc. Thanks! -S
I use waxed dental floss, (the single-thread type, not woven), over the cotton thread that Casey Burns used on my flute. It works great. Casey has agreed this is an appropriate thread to use.
I’m just lapping up the word-play! Nice to meet someone as warped and twisted as myself! I’m sure we could spin each other some good yarns… 
Embroidery “silk” - actually mercerised cotton, the lightly twisted kind - comes in 6 strands (each of which is a medium twist 2-ply). I unravel the skein, split it into two sets of 3 strands and use those, well slathered with cork grease over each layer as I wind it on. I’ve never had any serious problems with swelling etc., and it lasts 2-3 years on a flute that is frequently assembled and disassembled, longer on one less well used. It is relatively soft, so will not erode the wooden socket, a risk with some of the harder twisted threads or synthetics, and using the thin multiple strands it is easier to get a nice even lay. It comes in a huge range of pretty colours, but remember the grease will significantly darken the shade. See pics of one I did recently here
“Traditionally” a lightly twisted hemp/linen thread is used, but I’ve never found a source for it (not at any haberdashers, at any rate, however comprehensive their stock), though bagpipe makers seem to use it (usually in a garish yellow?), so it must be around.
…over the cotton thread that Casey Burns used on my flute
I don’t want to speak for Casey, but I’m fairly certain that he uses synthetic or linen thread, as cotton can swell if not properly greased. Casey?
I use poliyester gutermann thread the finer the better. I also sometimes use a fine silk thread. Put a little shellac on the tenon before wrapping the thread to keep it from slipping later. Cotton will swell when it get wet, and can crack the socket. Yu need to use a lot of wax, when using cotton.
Thanks for the input! So… I’ve been using cotton thread BUT have also been using a handmade cork grease which is made of two ingredients (one of them being beeswax). The ‘grease’ is on the hard side so I’m assuming that the beeswax is in the majority of the mix which would be waxing the cotton thread layer-by-layer. Hmm…
Not a big deal, they have been using cotton from the 18th century, no polyester back then… Just wax it every layer.
I have used a decent nylon thread sold by Gudebrod (size “EE”) for years. I was able to get this from Forrests Music in Berkeley CA where they sold it for tying oboe and bassoon reeds. But then Gudebrod, the manufacture, stopped making this size. I’ve been laying in a large quantity of remnants direct from the source, which will suffice until I try a different size or come up with a different source.
For wrapping thread I prefer something that doesn’t swell when wet, it small in diameter to not unravel easily yet large enough that one isn’t spending too long to wrap a tenon, and stuff that will pack down well for a firm fit once greased. There are other threads that work well for this, such as button threads, Linen, etc.
Happy Summer Everybody!
Casey
I looked for the Guterman thread here where I live, and couldn’t find any locally. I did, however find a comparable polyester thread at the local fabric store The brand here is Trusew, it comes in any color imaginable, and has 200 yards on a spool. If I recall correctly, I gave about 50 cents for the roll I have, and with only one flute that has threaded tenons, I’ll be using this spool for a while.
Oh yeah, one thing that you might want to look into is a fly tying bobbin. Looks like this:
I had one that I wasn’t using, but you can pick one up pretty much anywhere that they sell flyfishing and fly tying supplies. If I don’t use one of these, I end up with a huge snarled mess of thread.
Great idea, thanks for sharing! I’ll have to look into that, seems as though it’d be worth the hunt!
Yes that’s the stuff I use. You can get it from any bagpipe supply shop. Here’s how I was taught to wax it: Break off a couple of metres/yards and fold in half. Pull the doubled thread across some beeswax several times, - holding the wax in one hand and the thread down into the wax with your thumb while pulling it through with your other hand. The heat from the friction of the thread running through the wax will melt the wax right into the thread. Then wrap onto the flute, bagpipe or whatever.
When using this on a dry or almost dry joint eg bagpipe drones, you put on a layer or two of unwaxed thread first then the waxed thread on top. The unwaxed thread underneath stays soft and can compress slightly. Not so useful on a flute which gets too wet however.
Cheers
Graeme
Thanks, Graeme…first find your bagpipe supply shop!
Re wax - I just use standard music shop cork grease - the kind that comes in a “lipstick” or in a tub. I have beeswax but don’t use it for this purpose, having found years ago that it tends to build up on a joint (at least when used for lubricating an exisiting lapping) and get tacky and form a gunky mess on the surface, potentially jamming the joint or actually pulling the lapping off. I just wipe cork grease around the tenon bed before starting winding and then keep applying liberally as I go - I don’t bother pulling thread through wax first… on the lightly twisted cotton thread I use the pressure of putting the newly lapped joint together forces the grease into the thread - indeed the thread will go on taking up quite a bit of grease for a while. I’ve never had a lapping come loose from the bed wholesale as Jon’s advice suggests can happen, despite never anchoring the start of the thread in any way other than winding it tightly over itself. I would advise against using any tightly spun thread such as sewing cottons or button thread as they will not absorb whatever grease or wax you use so well and are much harder - hence my concern about erosion of the mortice surface. They also bed in less well and are more prone to getting dragged or scuffed and they require more care in lapping to create a good level finish. I’m not sure that a linen or hemp thread is any less water absorbent or prone to swelling than mercerised cotton, but none of them well greased should cause danger to the flute.
Hmm… The more I thought about that, the more I realized how, theoretically, that’s entirely the case re: keeping the tenons thoroughly greased, etc. Grease repels water and should, by theory, deter a moisture build-up due to its’ nature? I may be a bit off and it IS early however this does seem to make a lot of sense to me. I understand completely that the bore of the wood would be prone to moisture due to playing and depending on environment, etc. however my brain is currently telling me that the moisture would be on the tenons inside the bore of the flute and not on the female connector of the next section down which connects to the tenon(s)? I suppose, if you think about it, that moisture can accumulate basically anywhere on a flute (headjoint cork area, for example) if not thoroughly cleaned, etc. but (excuse me if this sounds redundant) my brain (it’s before noon so this is quite normal on my end here!) just is not putting 2 + 2 together as to how the moisture can possibly build up on tenons when the inner bore is normally where the moisture is going? slaps forehead! Back to bed for me! I apologize in advance for this post. 
When you push the male tenon into the female mortice/socket, the join line is never perfect between the shoulder of the socket and the end of the tenon - water can and will seep into the joint area through it, especially on the upper joints nearer the embouchure where there is more moisture. It will move freely in the joint at least as far as the edge of the lapping be it cork or thread, and will then soak into it, migrate by capillary action, etc., potentially causing swelling… In French style metal lined sockets there will be no water absorption by the timber of the socket, obviously, but in an unlined socket there could be some. The end grain areas of both the tenon and the shoulder of the socket are also exposed. Occasional proper oiling of the timber should give sufficient protection thereto. Greasing the lapping is to waterproof it to stop it swelling, to ensure an airtight join for good tone production and to lubricate it for the twist/slide motion of joining or separating the instrument’s sections.
Aha! Now it seems to make more sense, thanks!
This is probably obvious, but it really helps if the final bit of thread you use for fine-tuning the fit is a different color from the rest, so you can easily spot it and pick it off if the joints get too tight.
Hmm… Obvious to everybody but me, maybe, lol. I never thought of that. And here I was, patting myself on the back for being smart enough to use a Fly bobbin. 
Thanks for the hint. I’ll do that next time.
That looks like a cool set up, no more burned finger tips! I do like to keep some tension on the thread, when I lay it down.
So… Would the single-ply thread leave a harder threaded tenon and possibly cause cracking or would the singly-ply thread (ex. sewing thread [in my mind]) have any benefits?
Jon,
Thread tension is maintained in two ways. First by the spring action between the two legs of the bobbin that hold the spool in place. If you need more tension, then you adjust the tension by taking a wrap or two around one of the arms before you run the thread through the tube. Also, the good bobbins have ceramic coatings on the inside of the tubes, so that the thread doesn’t catch and snag.