An easy system for making a template and a mould

A method to create classical forms inspired by the work of the Cremonese masters

Makers reveal their special techniques

ALL PHOTOS ULRICH HINSBERGER

Over the years I have tried several different methods of making instrument moulds. Some ways were very innovative, such as the ‘multi-adjustable cross’ (no.1 on the picture); others were more sophisticated, such as the ‘Multiplex sandwich’ (no.2). I finally developed the method described here. Some of the following steps may be unfamiliar, but the final result is a classical mould. Using this system I end up with a rib structure that has a very lively and natural appearance, such as can be found on a lot of old instruments.

This article was written in collaboration with my assistant Maarten de Keukeleire. Working with young people is always very inspiring and beneficial for both master and student, as both can learn from each other. I really enjoy working with Maarten, who adds a lot of good ideas to our common projects.

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Drawing and plaster cast

Marking out the centre points

1 A nice mould starts with a nice design. We make a drawing using the system outlined in François Denis’s book Traité de Lutherie, based on a plaster cast of a Francesco Rugeri cello (1a). Then we use small clamps to fix in place a transparent plastic sheet 1mm thick. The plastic should not be too hard or too thick. In our case we used Makrolon 1mm from Bayer Polymers. Then we transfer all the centre points of the arcs with a scriber (1b).

Transferring the outline on to a plastic template instead of designing it directly on the wood of the mould gives several advantages. It’s easier to cut a homogenous material, and the template can be used to transfer the exact drawing on the left, right, back and front side of the mould. And after designing the template once, we can make as many copies of the mould as we want.

One trammel point end is sharpened

2 We use Veritas trammel points to transfer the arcs of the outline to the plastic. We sharpen one of the points to function as a knife, so that a real cut will appear in the plastic instead of a scratch line (2a).

To fix the needles we use an L-shaped profile made from stainless steel. Several lengths of 200mm, 500mm and 800mm allow us to draw all the sizes we need for a violin, viola and cello (2b).

An 800mm profile is used to mark the centre line

Now we use this self-made cutting tool as a compass and the underlying drawing as a guide to transfer the centre and radius of every arc (2c). To ensure a proper cut, we apply a certain amount of pressure and repeat each cut several times. Because we are using transparent plastic, it is easy to transfer all the centres and arcs to the reverse side of the template. We undertake the same process on the back.

Transferring the centres and radii

The plastic sheet is peeled away

Correcting the outline

3 After cutting the template from both sides, we ‘peel’ the finished template from the plastic sheet (3a). Then, if necessary, we can make slight corrections using files (3b).

A rectangle of willow

Dimensions of the mould

4 To make the mould we use a well-seasoned light wood, such as willow, poplar or lime. We prefer willow, which is offered by some tonewood dealers because a lot of makers prefer it for the blocks and linings. Working with solid wood is neither too heavy nor too unstable, as some may expect. Our oldest forms are more than 20 years old and still match their templates very well.

We cut four willow pieces to fixed dimensions and a local carpenter arranges them to form a rectangle as shown in 4a. Preparing this by hand is possible, of course, but takes more time.

Figure 4b shows the positioning and the size of the blocks. The lengths highlighted are as follows: (a) The width of the bottom-block; (b) The total length of the template minus the top- and bottom-blocks.

If the positioning of the four parts is well fixed on a flat surface during the gluing, the cut-outs will be nicely rectangular and ready to use for the top- and bottom-blocks. The spacing in the middle will function to fix the clamps while making the rib structure. It also makes the mould lighter.

Drilling

5 We fix the template with clamps exactly on the centre line (1) and fit it to the pre-made cut-outs of the top- and bottomblock (2) as marked in the photo. We drill two holes, each 6mm wide, through the mould to fix the template, and four more holes of 1.5mm through the template to mark the positions of the cut-outs of the top-, bottom- and corner-blocks.

The outline is transferred on to the willow

6 Now the template is positioned, we can transfer the outline on to the willow with a clear knife cut. Don’t be afraid of cutting into the template. If you make several controlled cuts using a sharp knife, and if you don’t make each cut too fast or too deep, you will be successful.

Marking the cut-outs

The top-block cavity still needs widening

7 We transfer the cut-outs for the corner-blocks with a scriber through the 1.5mm holes (7a), and mark the cut-outs with the knife in the same way as the outline. Only the width of the top-block cut-out needs to be widened to the final dimensions (7b), as the bottom-block is already defined.

Chamfering the edges

8 Now we use a bandsaw to saw out the mould, close to the knife cut. We chamfer the excess wood until the knife cut appears as shown in the picture.

The mould is shaped with a gouge…

9 We work down the excess wood with a chisel, gouge and/or plane, leaving enough material to finish later with the rasp and file.

…and a plane

Finishing the surface

The final mould

10 We finish the surface aligned with the knife cuts ( 10a). The result is a mould exactly fitting to the template with an even and rectangular surface.

Finally we stabilise the surface of the cut-outs with thin glue, to prevent chips when removing the blocks later on. To finish, we oil the whole surface of the mould excluding the pre-glued surface of the cut-outs. The oil prevents accidental gluing of the ribs to the mould, keeps it clean and makes it much more attractive (10b).