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  Making a Concertina Case 

 © John Bullar 2003   

Tricky things, hexagonal boxes. At least that's what I thought until I tried making one, when I discovered it is actually much easier than it looks.

I had to check the shape and size of the instrument to see what sort of case it would fit into. I borrowed it and sketched round the outside, including the buttons and handles.  

Start by setting your bandsaw table to 30 degrees off the horizontal so the blade passes through the table at 60 degrees. My six sides came from an 800mm (32 inch) plank, which I square -edged at 200mm (8in) wide. This method uses slightly less wood than you might expect as the outside edge of one side is cut from the inside edge of the next.

With the six sides cut, pull them together with a strap ready for marking out the shape of the top and bottom end pieces.

A pair of band cramps is ideal for pulling the six sides together around the two ends. I used some seriously heavy-duty Jorgenson models made from cast-iron and canvas. They were probably designed for pulling oak chests together rather than little instrument cases - but what holds a lot holds a little!

 To mark out the end shapes, temporarily clamp the six walnut side pieces together to act as a template, then use a knife end to mark the sycamore against the inside of the hexagonal tube this forms.

 I used fiddleback sycamore for the hexagonal top and bottom pieces because the musician who wanted this box, was also a fiddle enthusiast. It is wonderful wood to look at and has a strong natural ripple that looks like pleated silk when polished.

 Edge-joint two pieces of sycamore together so the ripples spread out from a joint line down the middle, fading towards the edges. 

Slot the side pieces with a straight bit down each top and bottom edge on the router table. This forms a rebate to receive the edges of the top and base panels. I would recommend test-fitting all the edges in their rebates before trying to pull the box together. This avoids any potential nasty surprises during the glue-up.

Cutting angled slots in across each butt joint requires careful alignment on a router table. I am lucky to have a sliding fence on the Jessem table to which I clamped each side of the box in turn. The alternative might be to sit the box on 30 degree wedges while sliding it along the fence.

Make the keys with the same dovetail cutter used for the rebate slots, set to the same depth. This time move the table fence up around the cutter. Cut the profiles for the pegs on the edge of wide pieces of wood, to keep the fingers well clear of the dovetail cutter. Thickness the wood to the width of the base of the rebate slot, and then slide down the router table fence to cut an angled groove on one side, turn over and slide again down the other side.

Careful adjustment should produce a profile on the edge of the wood that is a snug fit in the dovetail slots.

The peg material is then sawn off the edge of the wood and cut into 18 short lengths to make three dovetail pegs for each side joint. With the pegs glued in place, saw the excess off to reveal the butterfly patterns.

Woodworkers are often wary of using inlaid strip in solid woodwork, but with the aid of a mini-router and a bit of care, it is straightforward. Used sparingly, inlay lends a smart professionalism to the results. I prefer inlay made from simple stringing of a single wood such as ebony, especially when it is alongside the figuring of fiddleback sycamore.

Mark out the lengths with a knife and then chop them to size with a razor-sharp chisel.

A groove is routed to the exact width and depth of the stringing. The most important aspect is to start with a completely flat surface to rout the groove into - any hills and dales and you won't be able to cut an even groove. A fine artists' brush is ideal for getting glue in the base of the groove so it only sticks to the stringing.