Salve Håkedal, fiolinmaker
LIGHT CRACK CLAMPS
Cracks in violin plates should normally not need much pressure to glue, and it seems to me that the weight of the available clamps is out of proportion to the pressure they need to provide. Handling the plates with the clamps on is often awkward and possibly harmful to the freshly glued joint.
I have made some small and light clamps from materials that any violinmaker may already have in the workshop.
In addition to being light, this clamp has the advantage that it can (and should) be clamped to the plate before gluing.
Materials needed: - Medium hard wood such as beech or unflamed maple - Pieces from one cello and two violin adjusters The adjusters that will fit with the following procedure is: Wittner violin Uni model. Wittner cello Fix model. - Thin leather or rubber sheet - Any suitable glue
Step 1: Plane a piece of wood to 90mm lenght, 20mm width and 10mm thickness, and cut it into two peaces of equal lenght. Drill a 4mm hole through each piece from a narrow side with the center of the hole 11mm from one end, and then shape the pieces like this:
Step 2: Plane another thinner piece to ca. 41mm lenght, 23mm width and 4mm thickness, and cut it into two pieces of equal lenght. One of these pieces need a 4.5mm hole with center of the hole 4.5mm from the shortest edge and centered between the two longer edges. In the other piece this hole should be 3.5mm.
Step 3: The last piece of wood should be 20mm long, not more than about 7mm thick and exactly 10mm wide. One of the long sides can be a little chamfered or rounded off.
Step 4: Glue the pieces from step 1 and 2 to each other. The short edge of piece 2 should align with the closed end of piece 1, and the hole in piece 2 should fit against the open end of piece 1. Do not put glue over the open part of piece 1. The 'arms' must be able to move. Piece 3 should be glued with its narrow side onto one of the pieces 1, at the opposite side of piece 2.
Step 5: (The adjuster trick) You will have to slaughter 3 adjusters:
Step 6: To finish the assembly, pad the mouths of the clamp with thin leather or rubber, and put the adjuster screws into their respective tubes. To make the tightening of the clamp against the plate edges more comfortable for your fingers, chamfer the edges of the clamp at the point of the head of the violin adjuster screw.
The two pieces of the clamp can be taken apart by undoing the cello adjuster screw. This will allow you to put the clamp in place before you glue the crack, then take out the screw, put glue in the crack and then just put the screw back to set the clamp in action. And the clamp's weight is about 20 grams!
I use this clamp as an alternative to the usual brass clamp. One advantage is that it is light. It can also be used where the edges of the belly or back plate are at an angle to the lenght axis. And it allows removing the superfluous glue where the normal clamp usually gets in our way.
Materials needed: - Medium hard wood like beech or unflamed maple - Cork plate about 2mm thick - Plastic or plexiglas about 2mm thick - German silver string as used for bow pins - Thin braid nylon line - Any suitable glue
The shape and measurements of the parts are not important except the German silver string and nylon line should come out of the wood blocks as close to the surface of the plate as possible, so as not to exert harmful momentum on the edge of the plate. The cork should be narrow and placed so it only touches the bottom of the fluting, and not the ridge of the plate edge.
The plastic plate has four holes. One at one end which is to be hooked to the German silver hook. The three other holes should have a diameter a little larger than the nylon line.
Both wood blocks should be fixed to the plate edges with wedges on the under side. Then the nylon line is adjusted in the plastic plate so that when the plastic plate is hooked to the second wood block, the line will be just a little slack. The plastic plate can then be hooked off again and the line left loose while the glue is applied. When glue is applied and the crack is to be closed, the plastic plate is hooked on, and the long wedge is inserted through the loop at the first wood block to give the needed pressure.
When cleaning off the glue, the line can be rolled a little back and forth. And even if you need to use three or four of these clamps, there is not much weight added to the plate, so it can be handled quite safely.
This was published in the British Violin Making Associations Newsletter issue 44.
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