Preparing the wood and planing the pieces
 (image: 5.5

The carefully chosen pieces should be planed flat on the bottom surface. The pieces should not rock on your flat workbench.

Put them together and plane the upper tops as well to see clearly the where they meet.

Check, that both the pieces put together have sufficient width and height at the centerjoint.

Plane the sides at right angles to the bottom surface.

The initial planing of the joint edges can be carried out on a shooting board but later on you have to do the final planing by hand with the piece in the vice.

Clamp one end of the piece in the vice and support the other with a block of wood making sure that the piece wont bend while planing.

Check the inner edges with a square. Both edges must be at right angles to the bottom surface along the whole length. No twist. Use a source of light positioned behind the joint.

Bring the two edges together and check for gaps and rock.

If there is too wide a gap in the middle, correct this with a no 6 plane.

Once corrected, use a smaller plane to create a small gap widening towards the center. Just a little light must pass through, but it must be there. The ends have to be aligned as perfectly as possible, no rock, no light passing through.

Marking the outline
 (image: 5.3

Align the ribs with the back so that the centerlines match.

Mark with a 1cm long line the very top and bottom of the ribs.

Remove the ribs and make crosses on the centerline about 4mm inwards beyond the top and bottom marks you just made.

Drill through the whole thickness of the back two 2mm holes at those two points.

Realign the ribs so that they perfectly match the previous alignment, clamp down with two clamps and drill 5mm deep holes into the top and bottom blocks using the previously predrilled holes as guides.
 (image: 5.2

Now you can use the drill bits you used to drill the holes as locating pins to keep the ribs fixed to the back.

Once the bits are in place, remove the clamps and you can start with the outline.

Outline the contour with a scribe clearly marking the tips of the corners.

Take a washer, which you know will offset the contour by about 2.5mm and using a sharp pencil scribe again a parallel line around the ribs contour, this time always stopping 1cm short of the corners.

Finishing the corners
 (image: 5.0

The shapes of the corners will now be reconstructed by hand.

It is helpful to construct for each corner tip a guideline by projecting their angle towards the centerline.

Mark the tips about 2mm from the tip of the rib.

Finish the radii accordingly.

Sawing the outline
 (image: 5.1

Fix a piece of wood of approximately 60 x 7 x 5 cm to your bench making sure its protruding by at least 30 cm. Clamp your back upside down to the bottom of this wood.

Using a coping saw within 2mm of the outter pencil line. Make sure the saw is tilted so that you avoid undercutting.

Correct the outline, if necessary, with a rasp, downstrokes only.

Along the whole length of the contour scribe a line 6mm in height.

Now is the time to attach the plate to a plate holder using two screws. In our case this is a piece of wood about 60 x 30 x 2 cm.
 (image: 5.6

The screws must not enter the wood farther than 8-9mm and they are screwed in about 12cm in from the top and bottom edges, see fig. 5.6.

After the plate has been secured to the plate holder, clamp down the holder to the workbench.

With a pencil, mark the areas as depicted in fig. 5.7 and pare away the wood down to the 6mm line in those areas. Make sure you do not "enter" the waist of the plate more than 1.5cm.
 (image: 5.7

As you continue removing wood be extremely careful in the area of corners, as these are easily split. Be sensitive of the grain in those areas and apply only very limited force. Also make sure the gouge you are using in these parts is razor sharp.

Finalizing the edge thicknesses and creating the platform

Again, along the length of the contour, mark a height of 4.5mm using a scribe and after that a pencil.

Using a shallow gouge remove the wood along the edge roughly to that line.

Now is the time to finalize the outline of the plate. Clamp as in fig. 5.1 and using a file {downstrokes only}, make sure the outline is even, smooth and true to the scribed line.
 (image: 5.8

Mark a line along the whole circumference of the plate, 7mm in a the waist and 9mm in the upper and lower bouts, as in fig. 5.8.

Using a shallow gouge and a flat chisel remove the wood and create the platform not going beyond the marked line.

Make the platform as even as possible, resorting to a file, if necessary. Check for flatness and also for consistent thickness of about 4mm.

Take the purfling cutter make sure its passage is unblocked by wood, especially in the waist.

Cutting the purfling channel

Make sure again that the contour is perfect, without any bumps and that it flows gracefully and naturally in accord with the violin copied as this contour will no serve as the guideline for the purfling channel.

Carefully observe the distance of the purfling channel from the edge in the copied instrument. Normally it is about 4mm in but its final position is determined by the length and thickness of the corners. The purfling mitres must meet at just the right position to form the tip and bee sting.

The position of the purfling channel in relation to the edge and the corners can be tested first on the opposite side of the plate.

If using a double edge purfling knife, make sure the width of the resulting channel is enough for the purfling to slide in easily. Test this on a piece of spruce and maple to see the differences in both cutting and the resulting channel.

Everything adjusted, you can start marking the purfling channel with the purfling knife. Especially with the spruce top, it is important to first go very lightly otherwise the blades tend to get misaligned by the wood grain where they go parallel with it. Bear in mind that the channel itself is cut with a knife and the purfling knife is more of a marker, to create a rather shallow cut but with great precision which will later serve as a guideline for the knife itself. Again, go light, or you will loose precision. Repeat, until you are sure the groove is deep enough to guide the knife.

The final depth of the channel should be about 2mm assuming the thickness of the plate edges is 4mm.

Using the knife to cut the channel, go with light strokes followed by heavier ones. Avoid undercutting - the walls should be perfectly perpendicular.

Be extremely careful with the inner tips at the corners, which are easily chipped especially in spruce.

When you have reached a certain depth of the cut, remove the wood using a purfling pick.

Fitting the purfling

You bend the purfling stock as you would the ribs using a bending iron. Precaution must be taken not to overheat the purfling because the hide glue would melt and the layers would separate.

Also, the tight curves in the upper parts of the C bouts must be bent with utmost care as cracking will easily occur.

On the front plate, in the upper and lower bouts, the purfling can consist of 2 parts, as at the center it will be removed anyway. The gap must not exceed 8mm on each side off the center, though.

On the back plate, the upper and lower bouts should be made in one piece, if available.

Gluing the purfling

Have a suitable smoother and a damp cloth handy. Prepare a sufficient amount of medium to thin hide glue.

Work in the following order:
1. Glue the upper left corner, put in the upper left corner,
2. Glue the the upper bout, put in the upper bout
3. Glue the C bout, put in the lower corner, put in the remaining C bout
4. Glue the lower bout, put in the lower bout.

Note: In the C bout, the lower corner is glued set in before the remaining middle part of it.

Category: Building