The LBPS retains a number of makers who have agreed to act as ‘Technical Advisors’; they are available for consultation by members on pipe-maintenance questions; here Jon Swayne answers a question about thread posed by your editor

It's stating the obvious that the thread which is used to bind the various joints of a bagpipe performs a vital function. In fact the function is two-fold; one holds the parts together physically, the other keeps them airtight. How well it does this job depends a little on the condition of the pipes, but much more on how well the thread is applied. No doubt there are many ways of doing this job; here's how I do it.
When servicing pipes, I've found it's quite common to see a mixture of threads on one joint, where some maintenance has taken place. It could be yellow 'hemp' underneath, with maybe a few spaced turns of red cotton over that, perhaps some dental floss, and over the top a bit of PTFE tape. So what is the best thread to use?
I put hemp in inverted commas, because although we all say 'hemp', when you buy the yellow stuff, the label, if it has one, says 'linen'. I've no idea whether real hemp is or has been used, but from what I've seen of the real stuff I would say would be too hard and inflexible to be ideal for our purpose, though it may well be available in formulations which I've not seen. The thread that I believe is most commonly used, and what I use, is a yellow linen thread. It measures about 0.5mm in diameter, is fairly soft and quite loosely woven. The label on the reel in front of me now says 'Coats Barbour. Linen Single Shoe. Made in Northern Ireland'. It usually comes in two formats; one is a somewhat loose hollow ball; the other is a much tighter cylinder wound on a cardboard tube. The latter is rather easier to manage. Both weigh about 50grams. The first type can quite easily get out of hand in use. A tip is to pierce the lid of an empty clean jam jar from the inside of the lid with a sharp object such as a nail, to make a 3mm hole. Lead the free end of the reel of thread through the hole and replace the lid. Thread can then be drawn off the ball as required, without the ball getting lost under the bench and tying itself in knots. The second type can be treated in the same way, though you could equally place the cardboard tube over a spike in a small baseboard. You can get it from suppliers of highland pipes and accessories. I've also given another supplier at the end of the article.
Why do we use this type of thread? Simply because in general it has the best combination of properties for the job. It's neither too thick nor too thin, where ordinary sewing cotton would be regarded as too thin, and, say, crochet cotton as too thick, though it is quite possible to think of more extreme situations with very small finely made pipes or a very large medieval pipe where the latter materials might be more appropriate. Nor is it too hard or too soft. It has some resilience, which is important. I also say to those who enquire that it swells less with moisture than cotton, but this may be a bit of folklore I've picked up which has no basis in fact. I've not carried out any scientific tests, but it would be interesting to try.
In commissioning this piece, the editor described a recent experience where in attempting to tune a drone, the whole drone had come out of the stock. He observed that the same thread had been used for the stock joint as for the tuning joint, and wondered whether this was correct, and how you ensure that the stock joint stays tighter than the tuning joint. In fact in my opinion you use the same material for both joints, but there is a difference both in the method of application and the degree of tightness, which I will describe in what follows.
Here is what you need:
1.    Reel of thread in jam jar as above, under bench.
2.    Small bottle of liquid shellac with brush built into lid. This can be in the form of french polish or button polish, or you can make it yourself by dissolving shellac flakes in methylated spirit. The consistency should be about that of thin cream. The solvent used for gluing plastic models comes in the sort of bottle I've described, though these days it annoyingly has a childproof lid, which I advise you to disable.
3.    Sharp pair of scissors or knife.
4.    A small spike about 80mm long, 2 or 3mm in diameter coming to a gradual point (a bamboo kebab skewer works quite well) placed vertically in a small vice near at hand.
5.    A small block of wood about 120mm x 70 x 35 and a small baseboard about 150 x 80 x 15 (the latter is optional as you can simply use the surface of the table or bench at which you are working, if it is clean and smooth). Purpose explained below.
1.    The seating for the thread will usually be an area of slightly reduced diameter with 'combing' – incised lines at short regular intervals – intended to assist the thread in staying put. Paint this area with a light coat of shellac. It's very sticky but dries quite quickly. It will hold the bottom layer of thread and prevent it from sliding on the underlying wood. Otherwise it's not unknown for the whole body of thread to merely revolve on the tenon when you try to remove a joint from its socket.
2.    Holding the joint in  your left hand parallel to the front of your body with the tenon to be wrapped to the right (assuming your are right-handed), pinch the free end of the thread between your left thumb and the wood somewhere to the left of the seating.  Take a turn of the thread round the third or fourth finger of your right hand (this will enable you to place more tension on the thread), and feed the thread onto the tenon between your finger and thumb, starting from the extreme right of the seating. You are taking the thread over the top of the joint away from you in the first place, and winding in a clockwise direction from the point of view of the person sitting on your right. I aim to wind pretty much as tight as I can without the thread breaking. This type of thread is not nearly so consistent as sewing cotton and the breaking strain can vary quite dramatically over quite short distances, so it pays to be aware of that. You will be winding back over the thread coming from your left thumb, and after a few turns the thread will be trapped and you can if you wish adopt a more comfortable handhold; you can also trim the beginning end of the thread to within the seating area now, or leave it until last. Attempt closely spaced turns till you get to the left hand end of the seating. Continue winding on more turns back towards the right, perhaps paying attention to filling in any gaps left in the first layer.
3.    The finished binding needs to be reasonably flexible both in order to provide an airtight seal and also in order to take up small changes in the wood due to changes in ambient temperature and humidity. In my opinion three wound layers is normally a minimum for a new set of pipes. More than four layers is probably a waste of thread, but less than three does not give enough 'give'. I say 'for a new set of pipes' since the junction you are working on may not have enough room for more than two layers, so you make the best job you can.
4.    If you think you may have put on enough thread, you can now use your block and baseboard (or work surface) in 5. above. Grasp the block so that one of the 120 x 35 faces is downwards. Putting your weight on the block, roll the bound tenon under the block backwards and forwards so as to compact and flatten the surface of the thread. (I find it easier to stand up to do this, so that I can apply more pressure). It is surprising how a joint which seems tight when applied can become slacker over the first few months. The above process of rolling under pressure helps to bed the thread in quicker.
5.    Try the tenon in the socket. If you have put on an odd number of layers, the free end of the thread will come off the outer end of the tenon when the latter is pushed into the socket. If an even number, the free end will come off the far end which will therefore go into the socket first. The result in the latter case is that the thread leading to the ball or reel will cause the binding to be very slightly tighter than it would be if the thread were tied off and finished, and allowance should be made for that. It's annoying if after having finished as in 7. below, the result ends up too loose.
6.    If the fit is just slightly too tight, try rolling it some more. It may ease up. If it is too loose, apply more thread. At this stage it pays to pay attention to whether the body of the thread conforms to a reasonably accurate smooth cylinder, not wider at one end than the other, or at one point than elsewhere.
7.    When you have the fit you want, end with a whipped finish. The illustrations below from an old handbook of sailors knots given me by my father when I was about ten show the sequence of events, though of course in this case there is only one layer. Unwind say five turns and cut the thread from the ball a foot and a half or so from the binding; if you have ended at the left hand end of the tenon, lay the free end of the thread along the axis of the tenon, leaving the final four or five inches to the right, and trap it to the left of the binding with your left thumb; you now have a loop of thread hanging down; replace the five turns (however many you removed) over the top of thread lying along the axis of the tenon; there will be a small loop remaining, which you will remove by pulling on the free end of the thread. It ensures a neat and almost invisible finish, without any knots or lumps and bumps to get in the way of the smooth operation of a tuning slide. If you have ended at the right hand end of the tenon (as in the photo), after removing a few turns then you will trap the free end of the thread placing your left thumb somewhere in the middle of the top layer of binding, replace the removed turns, and finally remove what remains of the loop by pulling on the free end.

8.    When pulling on the free end to remove the loop, there is a tendency for the natural twist in the thread to cause a little tight bunch to form which will not be pulled through the final turns. If you use excessive force, the thread is sure to break, leaving not enough free thread to finish off properly. Here is where the spike in 4. above comes in. Before pulling to remove the loop, place the loop over the spike. Use the spike to keep a little tension in the loop as it closes, lifting the loop off the spike at the last moment, and it will avoid the formation of that pesky bunch.
9.    Of  course the fit of a drone in the stock needs to be tighter than the fit of a tuning slide, otherwise the drone will come out of the stock when you try to tune, or you will need two hands for tuning which is clearly inconvenient. To achieve this it helps when applying the thread to make as close turns as possible for stock joints; this makes the joint more compact and less flexible. For tuning slides, make the turns a little more widely spaced and more overlapping to give greater flexibility. Last year we had a student in the workshop for a few days who had already had a couple of years experience working for a pipemaker in Germany. When it came to applying thread, he asked whether I would prefer him to do it 'neatly' or 'chaotically' – an intelligent question, which expresses the above two possibilities admirably. There is definitely a case to be made for a little managed chaos when working on tuning slides.
Any other questions:?
1.    Thread dressing: in the past I've tried using waxed thread. It forms a compact mass which if the fit is good can act as a very effective piston. But it can be sticky, and usually needs greasing. I've come to the conclusion that unwaxed thread works better and lasts longer. On the other hand I feel that the thread on a mouthblown blowpipe tenon benefits from being greased with a non-drying grease, for example with petroleum jelly stiffened by melting together with a little beeswax, to help protect it from the effects of moisture.
2.    Ideal results can only be obtained if the pipes are well made and in good condition. In the case of antique pipes, the parts can have changed dimension to the extent that there is hardly any room for more then one layer of thread. Unless you are prepared to make alterations to the wooden parts, as I said above, you just have to do the best job you can, if necessary using a thinner type of thread.
3.    If the bores of the stocks and tuning sockets especially are not parallel and preferably smooth, it is impossible to get perfectly satisfactory results because the fit will vary according to the tuning position. In that case it is advisable to try for the best fit at the most likely tuning position.