Here's a brief description of many everyday repairs. Do you really know what's being done when these terms are mentioned? The following will give a better understanding of the repair process, and perhaps just how involved these tasks might be.
BRIDGE
The cutting of a new bridge involves selecting a new pre-cut blank of a width and type to correspond most appropriately to the instrument. The feet of the bridge are the two parts which touch the top of the violin, and it's imperative that these match the curvature where they sit. The job of the bridge is to transmit the vibration as cleanly as possible, and this even contact is critical. The bridge must stand correctly. The front face of the bridge is then thinned appropriately, and gently tapered down to a thin ridge at the top. The fingerboard end is referenced to mark and cut the final height, and the whole is planed, scraped and/or sanded to the final dimensions. The heart of the bridge, the wings, the feet thickness etc., are at the discretion of the craftsman, and will vary wildly from craftsman to craftsman!
DRESSING, FINGERBOARD
One of the most overlooked problems with stringed instruments is the condition of the fingerboard. It has been determined over the centuries that a gentle, even concave curve be followed along its' length, to allow clearance and free vibration at every note.
Why is it important? With an older instrument, just imagine a metal coated string constantly barraging a piece of wood on a daily basis. The organic material, usually ebony, loses the battle and succumbs to depressions and tracks left by the strings. Eventually, the string will start to slip into one of these crevasses, instead of sitting cleanly on the surface, and a slight "blurring" of the sound occurs with false notes slipping in. The correction involves re-establishing the correct curve, and carefully planing, scraping, sanding and polishing the surface. The utmost care must be taken to use all tools on long, even strokes so as not to end up with "hills and valleys" again.
NUT
The nut is the small rectangular block that sits at the top of the fingerboard, directing the strings into the peg box. A correctly fit nut should blend seamlessly with sides of the fingerboard, and stand just high enough above it to accommodate the string slots. Much has been written about the merits of nut profiles, but for us a rule of thumb might be that the string sits about one half of it's own diameter above the board. Too much less, and a buzz occurs. Too much more, and unnecessary pressure is needed to compress the strings. A new nut requires the old one to be removed. Once done, a new piece of ebony is offered to the site and marked accordingly. The top of the nut should be cut to guide the strings as smoothly as possible down into the peg box with no harsh angles. This can take the form of a soft curve back and down slightly, but can vary from craftsman to craftsman. We still favor a quick stroke with a soft pencil in each slot to allow easy slippage of the string at this point.
PEG
A fit peg should be of a hard material, most usually ebony, but sometimes rosewood or boxwood. The French used rosewood for decades as seen on fine older instruments. Top of the line European instruments used intricately carved boxwood, but still ebony is the primary wood for this job. There is seldom an opportunity to "fix" poor pegs by adjustment. Re-establishing tapers with new fittings is the most efficient and warrantable method.
The scroll is examined for the best approach, often requiring enlarging the holes slightly to make them uniform. Only the absolute minimum amount of wood should be removed to achieve the objective. If the holes are already too big, the job requires peg bushings to allow the smallest profile peg to be used again.
Once the appropriate sized holes are made, the pegs are cut to fit in a shaper. This looks like a large pencil sharpener with two, three or four holes to shape the peg to exactly the corresponding size. Care is taken to burnish the holes in the scroll, and the pegs are tried in the holes and gently turned until marks appear. The high spots appear shiny, and can be scraped gently until a perfect polished band appears around the peg at the points where the scroll makes contact. A bearing agent is used to ease the smoothness of the peg turning, while still allowing it to stick in position when required. This can be a sensible proprietary compound such as the Hill peg compound.
The ends of the pegs are softly domed by sanding and polishing so that the tip simply fills the exposed hole, not protruding. Each peg then has a small hole drilled appropriately to accept a string, and the work is complete.
SADDLE
The saddle sits on the edge of the top of a violin, acting as a bearing for the tremendous load from the tailgut of the tailpiece. The small strip of ebony (mostly) evens out the load across the endblock area, and elevates the tailgut enough for the tailpiece and any of it's fittings to clear the top of the instrument.
Wood moves. It expands; it contracts. Therefore, a tiny gap at each end of the saddle is not only permissible, it's common sense. In the absence of this, the pressure can build around it enough to split the top under the tailpiece - a very costly repair. For the purists, a soft black wax can be rubbed in to make it look smoother; this simply oozes out under pressure when the going gets tough. .
CRACKS
Although the word strikes terror into a player’s heart, it’s most important to know that an instrument moves by contraction and expansion routinely. In the world of cabinet making, allowances are made all the time for such movement, with certain joints able to creep just a little, seasonally.
Not so with violins. We glue on a back and a top, all the way round with a perfect joint, and expect it to stay intact! Generally, with careful humidifying, the wood will stay about the same size and not give trouble. Difficulties arise when an instrument is exposed to moisture, then quickly dried in another environment, and the wood fibers try to tear. An example would be in winter time, when a violin is carefully stored in a home with both heat and some added moisture from a house or room humidifier. All is well until it’s taken to a school or church hall where scant attention is paid to humidity. The instrument quickly loses its moisture content, and as a result, shrinks. Something has to “give”, as various parts move differently because of their shape and absorption properties. There are two possible outcomes; a glued seam (where the rib meets the top, or where the rib meets the back) will open, or the pressure will force a tiny crack, most often in the soft part of the grain of the top, or table, of the instrument.
Sadly, some instruments come in with top cracks, and with the seams of the violin very much tightly glued in place. Most common are the cracks which emanate from either end of the saddle, extending up the table an inch or two. Usually, the ebony saddle has been carefully fit to the edge, surrounded seamlessly by the delicate spruce of the table. Moisture will have a pronounced effect on the spruce, but the stalwart dense ebony barely moves, creating stress points.
On cheaper student instruments, we try to be imaginative and minimize expense when faced with table cracks. It’s possible to glue some cracks from the outside, and put a few light spruce “cleats” into position through the “f” holes across the crack to reinforce the wood. . However, the only warrantable restoration is to remove the top of the violin and secure the crack with much more precision.