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I have grouped cutting, hollowing, gluing and clamping together as it is a process I do in one session. Although the wood is seasoned, there is still moisture init it and it may still twist or warp, especially as the bore is removed. The wood grew, supporting its own structure, and in making the didgeridoo this structure is disrupted with the tension in the wood, designed to support itself, suddenly no longer there. The didgeridoo is in two halves and each halve may distort independently. This can make a neat, almost invisible joint almost impossible. To reduce this risk I do everything together and will not start if I do not have time to finish.
If it is not possible to complete this process in one go, then try to keep the wood as stable as possible. Treat both halves the same. I have read and been told, though I have not needed to do so, myself, that covering the wood in plastic helps keep it stable, as does coating the wood in PVA. (Bear in mind that the PVA won’t come of later on and will already have dried on the gluing surface, unless it is removed, which may adversely affect the quality of the join.
Cut
Before I laid hands on a bandsaw, I tried as many (lots) of hand saws, from frame saws, reciprocating saws, ordinary hand saw, Japanese hand saw (Hassume). Of these the Hassume came out on top, with a good clean cut which was easily achieved, however it was not easy for cutting the tighter curves in the timber due to the depth of the blade.
Setting the bandsaw up is correctly essential if you want a hassle free cut, ensuring a sharp blade is used, with the cutting speed and height adjusted correctly. Allow enough space, both sides of the blade for the wood to go and consider how it will be supported. The blade thickness and number of teeth are important. The wider the blade, the smoother the cut, but is offset by not being able to cut such a tight radius as can the thinner blades. The number of teeth in an inch of the blade is crucial as well. The more teeth the cleaner the cut, but is offset by the more teeth per inch of blade the thinner material you can cut (as the teeth clog with the waste material). For most didgeridoo’s I use a 5/8” blade with 4tpi (teeth per inch).
If the piece to be cut is fairly straight it makes it a darn sight easier to feed through the saw as a smooth motion can be adopted. If the piece has significant twists and curves I would recommend practicing how you are going to do the cut. With pieces that are other than straight, I mark where I want the cut to be. Also consider how you are going to hold it if, for example it has a large or flared bell, one end will be very heavy!
Feed the wood through the bandsaw, taking care to keep it level and straight. It is easy, as the cut progresses, and your grip on the wood changes, for the wood to rotate. This is exacerbated if the cut is not in the middle of the wood, the downward force of the blade will pull it in one direction. I have finished with some very interesting pieces of wood almost looking like a corkscrew. Another thing to be mindful of when cutting the didgeridoo is pushing to hard and causing the blade to twist. When this happens, the cut will veer off centre and you will end up cutting a strip from the wood, rather than cut it in half. I have experimented feeding the wood thin and thick end first to see if the wood cuts better one way or the other but can’t say as I’ve noticed the difference. I cut the wood thick end first only because I find handling the wood easier.
Marking Up
Having cut the didgeridoo in half, it is nearly ready to hollow. Different people have different opinions as to the shape of the bore and what makes what sound. I started out marking up the bore with parallel walls the entire length and relied on the outside shape of the wood to dictate everything. The thickness of the walls were varied to experiment with resonance of the wood, i.e. if Sweet Chestnut is lighter in mass than Yew, then maybe thicker walls would compensate for this.
One experiment I conducted was to take several didgeridoo’s, all made with the same shape, but changed the internal dimensions slightly with each one to see what difference it made. This process is still ongoing and I’m keeping the results to myself for the moment!
To help draw parallel lines along the edge, hold your pen or pencil in a fixed position using your fingers to create the thickness you want, see photo.
Alternatively a little jig can be made from card/plastic/metal etc, bent to a right angle, then a hole placed the to how wide you want the didgeridoo walls to be. Then place your pen or pencil in the hole, and, holding the jig against the edge of the wood, run it up and down. See diagram and photo.
Hollowing the Bore
The fun bit.
The arbortech is lethal, take great care and treat it with respect. Keep it sharp – using it blunt needs more force, and the wood tends to snag and burn rather than cut the wood. When sharp it cuts through wood like butter. I sharpen the arbortech prior to hollowing every didgeridoo. Practice on a spare piece of wood if you have not used it before as it takes some getting used to.
The didgeridoo half is clamped onto a couple of carpenters horses that I made out of 4”x2” (100x50mm) timber. I place a ‘V’ block on each horse. Each V block has two V’s cut in it, one large, and one small. This is so I can turn the didgeridoo around to suit. Also helps keep the top of the clamp out of the way.
Once the wood is securely clamped in place, I start at the bell end of the didgeridoo. Initially I cut a shallow groove at the edge of the wall, then in ever deepening parallel cuts work towards the middle. I then go to the other side of the wood and do the same. At this stage it is rough working and clearing out the bulk of the timber. When I have neared the size I desire, the arbortech is used very gently, giving a good finish. Some didgeridoo’s will have twists, or turns, knots or other features that the arbortech can not reach. When this is so, I use chisels and gouges to hollow the bore.
Once I have completed the end, bell section, I move the clamps and work my way up the body of the piece to the mouthpiece end. At the mouthpiece, I already have an idea as to what shape I want but I purposely cut the bore narrower. This will allow me more accurate adjustment after the didgeridoo is glued back together. The same process is adopted for the other half. Once both halves are completed I check them over and feel for any imperfections, look for any wood that is loose, damaged, or may otherwise cause problems later. In most cases I finish the bore with a gouge, because I like to get it ‘just so’.
One thing I can not stress enough is to check the work at EVERY stage. Every time I make a cut I check the depth by hand, and where possible by eye, looking at it from different angles. This is so important as it is easy to cut too deep, too shallow, and not follow the contour of the wood.
How you cut the wood, is up to you and how comfortable you are with the equipment. This is how I do it, and hope your find it useful.
Burning the Bore
Once the bores are hollowed and I am happy with the results, I use a blow torch to scorch the inside of the bores. I do this for several reasons. Firstly there may be fine strands of wood that I have had difficulty removing, for example in areas around knots, and secondly the heat causes the surface of the wood to harden and thus provides a cleaner surface for the air to travel down when the didgeridoo is played. Another thought of mine, though I do not vouch for its validity, is that because the heat hardens the immediate surface and therefore it has a far lower moisture content, it is more receptive to a sealant when/if the bore is sealed.
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