With that all being said, here's the outline of how I expect to proceed.
Step 1: Disassembly and Assessment
Disassembly might seem like an easy process. In some ways in can be one of the most fun steps. Destroying things is more fun than building them, with english horns as much as Legos, and the "organized destruction" of an instrument tear-down is one of my favorite parts of an overhaul. But it's a much more methodical process than, say, the crushing of a lego house with a pair of size 12's. First of all, disassembly is the time when parts are most likely to break or become damaged, especially if they haven't been moved in a long time. This is especially true of screws, which are almost always made of steel and therefore prone to rust. I've ruined the heads of many screws trying to extract them because I wasn't patient enough to work them out properly. On an instrument like this one, with long hinge rods and tiny shaft lock screws - which are as fine as watchmakers' screws - there are plenty of places for things to get stuck. After removal, screws need to be individually set in a screw board to insure they each go back in the right place. Complex mechanisms need to be diagrammed for reassembly, parts need to be measured, and notes need to be taken on what's missing. Fortunately, I've gotten most of the key disassembly done with no major issues. All of the screws came out with minimal coaxing, and only one pinned rod is really stuck. Next, though, I'll need to take notes on all of the pads and key corks before removing them prior to cleaning. The socket rings and liners will also need to come out for crack repair, and it may even be necessary to remove the octave key wells (which the octave pips thread into), but I really hope not.
Step 2: Cleaning
Cleaning involves three distinct processes: cleaning the wooden body, cleaning the metal keys, and cleaning the steel screws. The body will need to be cleaned by hand to remove dirt, organic material, and old oil. The keys can be cleaned in an ultrasonic machine (read more about that here) to remove surface deposits, corrosion and oil, followed by a silver dip to remove tarnish and hand-cleaning the insides of all hinge tubes and aperture holes. Screws can be polished with a fine abrasive to remove rust and buildup, and some will get a bath in WD-40 or penetrating oil.
Step 3: Body Repair
The most visible part of body repair is filling cracks and holes. This step will also involve inspection of tone hole edges to check for chips, and if necessary filling and leveling to create a smooth, consistent edge. Since the instrument will be padded with cork pads, it's imperative that the tone holes have no imperfections through with air can escape. Cork pads don't compress or deform to the shape of the tone hole rim, so even a small dip in the rim can cause a leak that will lead to problems.
If it's possible - rather, if I have access to the necessary tools - I may also use this step to replace the decorative section of the crown. The alternative to that would be filling in the chipped areas, but replacing it will create a much nicer final product.
The final step of body repair, once everything has been filled in and finished and the joints are checked for airtightness, will be to oil the body. In an instrument as dry as this one - and it will likely be dryer after more oil is removed during cleaning - the best option seems to be an immersion oiling, where each joint will soak in oil for a few days until it's soaked up as much as it needs. Oiling needs to take place last because oil in the wood can prevent glue from adhering, and gluing is a big part of crack and tone hole repair.
Step 4: Key Repair
As keys are moved up and down tens- or hundreds-of-thousands of times over the course of their lives, they inevitably wear. Any time two pieces of metal rub against each other, they will start to wear out, especially when one metal is softer than the other. In this case, the relatively soft silver in the keys is rubbing against much stronger steel in the screws. On keys held by hinge rods, the result is that the hinge tube (the part that the steel rod goes through) develops end play and lateral play.
- End play can be seen on just about any woodwind instrument, and is visible where a key can be moved back and forth between posts. Usually the movement will be minimal, less than a millimeter, but any amount of end play can make it impossible to do precision work on an instrument.
In this overhead diagram, the direction of end play is shown by the arrows. The gray gap between the edges of the key and the posts represents the hinge rod, which goes all the way through the key and will be visible in these gaps when end play is present
- Lateral play occurs when the diameter of the hinge tube gets enlarged by constantly rubbing against the steel rod. It's less easy to spot, but can be seen when a key can be wiggled on the rod. Lateral play is perpendicular to end play.
Even if a key is tight between the posts and has no end play, as would be the case in this diagram, there can still be lateral play.
On keys held in place by pivot screws instead of hinge rods, the process of removing play is much simpler. Since a key held on by a pivot mechanism is basically held in place by two points (the points of the screws on either end), it's just a matter of making the points of the screws snugly fit into the receivers on the ends of the key. This can be accomplished by making the screws go in further, either by modifying the screws themselves or countersinking the posts into which they thread. This takes care of both end play and lateral play.
Other parts of the key repair process involve straightening bent keys, and in this case manufacturing parts that have been damaged or removed. It'd be great to have a functional and attractive left hand F mechanism on this instrument, which means I'll have to build a new one from scratch. Other parts will have to be replaced or cleaned up to make everything functional again. That's an extensive and involved process that will get a thorough explanation later, when I actually do it.
Step 5: Padding
Once the body is prepared and the keys are fit and functional, it's finally time to do the part that most people think of as central to an overhaul - padding. This also involves installing all new key corks and tenon corks. Cork pads will be floated on a stiff, high-temperature glue that will hold them firmly level for as long as they last. The glue is not susceptible to environmental conditions such as cold or humidity, and so the precise orientation of the pads to the tone holes should ideally never change. If the tone hole edges are properly prepared and the keys are fit well, padding can actually be a somewhat quick and simple process. It's critical to have three levels when padding: a level tone hole, a level pad surface, and a level pad cup. Nowhere is this more true than when working with cork pads. Cork pads are the firmest and least forgiving pad material used on woodwind instruments. Ideally, one should also strive to have even pad protrusion - the height of each pad that's visible below its pad cup.
Step 6: Regulation
Regulation means controlling the various mechanisms that cause more than one pad to close at a time. This can be especially tricky on oboe and english horn, where some mechanisms close up to four pads at a time. For instance, the low C touchpiece closes the low C pad, the E and F pads when that key is open on high notes, the F resonance pad through the E pad, and when moving from Eb, it also closes the Eb pad. It's almost never called upon to actually close all of these at the same time, but they all have to be precisely regulated so that it could. Having level pads is key to effective regulation, and it's made much easier on an instrument like this that has regulation screws.
Once regulation is done, any slop in the mechanisms has to be dealt with. If one key starts to close, then catches one of it's dependent keys on the way down, that's known as lost motion, and is undesirable in most cases. Lost motion makes an instrument's mechanism feel unresponsive and "clicky." When one key closes another key (known as a dependent key), the ideal setup is that the dependent key start moving with the primary key as soon as it's pressed. This is achieved through properly trimming key corks and having consistent pad protrusion. A mechanism with no lost motion feels tight and gives the player positive feedback and a feeling of firmness when they close a key.
Step 7: Play Testing
Oh yeah! At some point, this project will produce something that's intended to make sound! Play testing is in some ways a rewarding process. Making sounds on an instrument that you've fixed gives a feeling of payoff and gratification, especially if that instrument has been unplayable for a long time, as this one has. It can also be a trying process, though, as it forces the technician to listen and feel carefully for problems with the instrument. Even an instrument that's been carefully worked on will have some sort of issues come up in the play test, and it's the mark of a professional to be able to hear those problems, find the faults in their own work, and figure out how to fix them. The technician must be their own worst critic in this stage.
Step 8: Lost motion
Once issues are dealt with and regulation is done, any slop in the mechanisms has to be dealt with. If one key starts to close, then catches one of its dependent keys on the way down, that's known as lost motion. In most cases lost motion is undesirable. It makes an instrument's mechanism feel unresponsive and "loose." When one key closes another key (known as a dependent key), the ideal setup is that the dependent key start moving with the primary key as soon as it's pressed. This is achieved through properly trimming key corks and having consistent pad protrusion. A mechanism with no lost motion feels tight and gives the player positive feedback and a feeling of firmness when they close a key.
Step 9: Voicing
Voicing is the step with which I have the least experience, and involves listening for tonal inconsistencies in the instrument and tuning issues with particular notes. If certain notes "pop" or sound muffled or certain notes are noticeably out of tune, they are dealt with in this step. Voicing can involve changing the height of key openings or placing material inside tone holes to adjust clarity or tuning. It's a meticulous process and requires great patience. One can expect a lot of frustration and minor setbacks at this point in the game, because the adjustments have become so fine.
Step 10: Profit!
Well, maybe not in this case, but if all the other steps are done well, the instrument should have a long playing life with minimal regular maintenance.
