This instrument is fully mounted in elephant ivory. Every ferrule, ring cap, projecting mount, bush, sole, etc. is threaded onto the wood for a lifetime fit. This time-consuming and precise workmanship is completely hidden by the time the pipe is finished.
Choosing the wood for a high-end pipe is the first step. All the wood to be used has already been bored and intermittently reamed long before the wood is selected. It is again reamed to spec. before the pipe is made, and again after it is finished. If I don't like the way the bores look after the first reaming, it is rejected. I choose the wood based on age, density, color, tightness of grain and figure. Care is given to make sure that the tenors match using the same criteria. Because the wood selected is in its 'roughed' shape, choosing the wood takes a fair amount of time. I like to choose the wood and then do some preliminary finish work and turning to each piece to make certain that the wood is going to meet my expectations when finished. Sometimes the wood in its 'rough' shape does not look at all the way it does when it has had a lot of finish work done to it. I'll keep rejecting pieces up until the time the pipe is finished. I make one pipe, one piece at a time. Every instrument I make gets my undivided attention until it is complete.
After acquiring the ivory for this set, and doing some basic turning and threading to it, I didn't like the way some of the parts matched for color and general appearance. In particular, I thought the original ring caps and bushes were not a perfect match. The bushes were just a shade too light for the ring caps -- even though the bushes came from the same tusk. I purchased some more ivory for use as caps and bushes and was delighted that they were a perfect match for the ferrules and other ivory used throughout the set. The ferrules on the stocks have an unusally complex pattern that is not often seen on elephant ivory. All ivory is CITES approved pre-ban stock and is very, very old by the time I receive it. Cracking and/or checking is almost never a problem with elephant ivory. Unlike 10,000 year old mammoth ivory that is often problematic due to its age.
Every ferrule, ring cap, bush, projecting mount, sole, mouthpiece sleeve, etc. on Atherton bagpipes is threaded. Threading all these parts was once commonplace on all bagpipes made by the Great Makers. The average modern consumer has no idea that these parts are supposed to be threaded. Because the threading is completely hidden, most have no idea whether or not the parts on their pipes are threaded or not-- until the parts start falling off the pipes. (There is a way to determine if parts have been theaded by simple visual inspection, but I won't include that information here).
For the most part, threading has been abandoned by most makers today because of the enormous amount of time and skill (translation= cost) required to do it properly. Traditionally, the internal and external threads cutting into the wood and other raw materials were done using a technique called thread chasing. All the threads were cut by hand. I should mention that most (if not all) threads cut this way are slightly tapered - some more than others. Cutting tapered threads makes fitting the parts much easier than cutting a perfectly straight thread. The taper is also advantageous for fitting the parts together. Because the parts are fitted incrementally (fitting the pieces together many times, screwing them on and off, and checking for fit) a slightly tapered thread helps not to damage the wooden threads, as at some point the thread comes to a point of being infinitely thin.
Ivory (and artificial ivory) projecting mounts, ferrules, ring caps, etc. were almost always threaded on the classic makes of pipes. Metal (silver, nickel, etc.) parts were not frequently threaded, as the makers at that time didn't incorporate the machinery necessary to do so.
One would think that in today's high tech world with machinery capable of holding a .0001 tolerance that all parts, then modern makes of bagpipes would be threaded, especially given the huge advantage that threaded parts have over non-threaded parts. The reverse is actually true. Very few pipes made today have threaded parts. Unfortunately, all that expensive technology is used to crank out parts at a breakneck pace with little regard for the longevity that threading gives a bagpipe. The machinery is simpy used to make parts faster, not better.
I should mention that threading is not a panacea for parts coming loose. With Highland Piping being so popular and pipes being shipped all over the world and being subject to all sorts of climates and extremes, it is possible for a threaded and glued part to work its way loose (though it is rare). In this case you can simply un-thread the part, add a drop of glue, and you're good to go.
The salient point here is that a maker who is concerned about making a pipe that lasts, threads as many parts as possible. A maker who threads, is a maker who cares about their product. There is no good reason to abandon a traditional technique that is empirically proven to make a better instrument.
Traditionally (for nearly 200 years) threads on bagpipes are a 55 degree pitch, or British Standard Whitworth. Atherton bagpipes uses only BSW threads.
The thread pitches used on the instrument pictured below are:
Ferrules- 24 tpi
Projecting mounts- 24 tpi
Chanter sole- 28 tpi
Ring Caps- 32 tpi
Bushes- 28 tpi
Mouthpiece sleeve - 30 tpi (inside) 30 tpi (outside)
Mouthtube (black delrin) - 20 tpi
Blowpipe -- 24 (external) 30 (internal) 30 (external)
The sizes I use have been arrived at through 15 years of making bagpipes and collecting empirical data. A lot of thought and care has gone into the decision to use these sizes. Having worked on many, many classic sets of pipes, and having the advantage of hindsight-- of being able to see the pipes 100 years after they were made -- I've been able to to assess how they (in this case the threads) could be improved upon.
It was very common on 19th century sets to use very fine threads on the bushes and ferrules. Thread pitches of 32, and 30 tpi were very common. The problem with using such a fine thread pitch is that the threads do not give much 'bite' into the wood. In other words, when 50 years have gone by, and the wood has naturally lost a bit of moisture and shrunk a bit-- the bush or ferrule may work its way loose. This is perfectly acceptable when considering that the maker went to the trouble to thread the parts in the first place, and that the pipes are quite old. (There is no excuse for this happening to a new set, however.) Having the advantage of seeing the result of age on a instrument, one can then assess how it can be improved-- even if only incrementally. I use 28 tpi for bushes, for example, rather than the 30 or 32 used 100 years ago by most (but not all) makers. Yes, the devil is in the details.
More than any other part of the bagpipe, ferrules are under stress. They are not mere decoration, they have a function. All ferrules on Atherton bagpipes are threaded. Silver, nickel, ivory, artificial ivory, horn, wood, etc. Every piece is threaded.
When using threaded metals (silver, nickel, etc.) the metal is fitted to the threaded wood and glued. Because the metal is so strong, it can be threaded on fairly tightly, thus binding the wood and providing a very strong support with uniform concentric pressure. This small bit of pressure is needed to protect the wood from cracking when a hemped tenon is inserted into a ferruled part. Metals make a great ferrule material. Threading the metals make for a great way to keep the ferrules in place, doing their job of protecting the wood. As mentioned earlier, metals were infrequently threaded 100 years ago(though some sets with threaded metals have survived) by pipemakers because they didn't incorporate the machinery necessary to do a proper job of it. Given the fact that they threaded everything else possible(ivory ferrules, for example) I'm sure they would have enjoyed the ability to thread metal ferrules and caps.
It is very important that real ivory and/or artificial ivory (and wooden) ferrules be threaded. It was traditional for pipemakers to thread these materials for well over 100 years. Due to modern mass-production techniques and the streamlining of the once traditional, the threading of ferrules is quite rare on most modern bagpipes. (though it is the norm on well-made bagpipes)
Threaded ferrules provide uniform concentric pressure on the wood underneath them. This is also known as 'hoop stress'. This hoop stress provides enough inward pressure to help stop the wood under the ferrule from cracking. I should mention that when I fit a threaded ferrule, it only takes a few hours or a day for the once concentric bore to 'crine in' by just a few thousandths of an inch. This means that the ferrule is doing its job. A simple reaming of the part back to spec. brings the part into concentricity once again.
The threads on the wood also mean that the force on the wood(from a hemped tenon) is spread over a larger surface area. This means that the actual pressure on the wood is reduced, even though the force remains constant. (consult any physics text for verification) Ferrules that are merely glued do not provide this advantage.
Ring Caps and Bushes
Ring caps and bushes on Atherton bagpipes are always threaded. Leaking bushes and ring caps are common on inferior bagpipes, and make for an instantly unsteady bagpipe. Again, 200 years of tradition have proven that threaded bushes and caps are a hallmark of quality.
There are 4 threads back to back between the ring cap and bush on each top. The inside threads on the wood, the outside threads on the bush, the inside threads on the ring cap, and the outside threads on the wood that gets fitted to the cap. All threads are tapered. It takes an enormous amount of skill to thread all parts (by hand) and have the end result look like a seamless flow from ivory to wood and then to ivory again. The smaller thread pitches used (30 and 28 tpi) help to facilitate this illusion.
If there is even the slightest amount of imprecision when the parts are threaded and glued together, there will be a gap between parts. When done properly, close inspection reveals the threads at some point coming to be infinitely thin and the cap and bush material become somewhat translucent. In other words, the wood can be seen clearly through the threads of the cap and/or bush.
Some thoughts on Aesthetics
This is a tough subject to put into words so for the purpose of this writing I will keep it limited to this particular set of pipes.
Stocks: The bass stock is the largest in diameter and has the longest ferrule @ .740
The tenor stocks are considerably thinner and have just slightly shorter ferrules, by approx. 1/16th".
The BP and PC stock are a bit thicker (to accomodate bag sizes) and have the same length ferrule as the tenor stocks.
Traditionally (as in 19th century pipemaking) the stocks may have one or all of these details.
The elephant ivory ferrules have a MacDonaldesque 'stepped bead'. This stepped motif is repeated throughout the set on the ring caps and on the bold bulb mouthpiece.
(I was lucky enough to restore a priceless known Donald MacDonald pipe (in pristine condition) a decade ago.)
The bass top and bass middle joints' ferrules match the length of the bass stock ferrule, though they are smaller in OD.
The tenor top ferrules are the smallest in OD and are also the shortest in length. A feature found on 19th century pipes.
The tenor top bushes have a single cut in and one scribe line.
The same single scribe line is seen just under the combing on the bell. The combing on either side of the bell is 26 tpi, and is just one tooth less than the same combing found on the bass. Just a very small detail to distinguish the tenors as unique--
The bass top bush has a single cut-in and a double scribe line. The same double scribe is found just under the comb on the bell. Why two scribe lines? Because it's the bass.
The ivory projecting mounts are matched as follow:
Bottom mounts-- the bass bottom mount is the largest, being just .020 larger in OD than the tenor bottom mounts. (This is a 19th century tradition on many exquisite sets.)
The BP mount is the same OD as the tenor mounts.
The tenor top mounts are just slightly smaller diameter than the bass top mounts, though they are consistently the same length.
The bass bottom top mount is just a bit smaller in OD than the bass middle top mount. On very old pipes it iscommon to see the bass mid joint with a much larger projecting mount than the bass bottom top mount, but I tend more towards the subtle.
As metioned previously, all fitments are threaded and then glued. I will use 5 or 6 different adhesives on one instrument -- with each adhesive used for gluing a different part of the pipes.
After much experimentation over the years I've settled on a combination of basic hide glues, aliphatics and epoxies as well as the more exotic methacrylates, acrylics, and resins -- requiring an etchant, primer, and activator.
There are many differing materials that need to be bonded. Wood and metals, ivory and wood, artificial ivory and wood, acetal and wood, acetal and artificial ivory, etc. It takes many different kinds of adhesives to get the job done. For instance, I'll use one type of glue for threaded silver ferrules being bonded to wooden threads, and a completely different adhesive to glue silver tuning slides to wood. Thread pitch (small or large) may also factor into what type of glue is used. Some may call this obsessive, but it's just a properly made bagpipe.