|Western concert flute (Photo credit: Wikipedia)|
Now the body of the flute is quite intricate. There are 18 keys on the body of a C flute. The number of springs can vary somewhat but it is around 13 give or take.
The springs can be made of steel or copper or bronze. Steel is the best and easiest to work on. They have to be adjusted for the right strength. They can be too weak, which can cause closing problems and leaks. Also, they can be too strong which can cause the same problem. You have to get a feel for the exact strength and that can vary from flute to flute. Some springs need to be replaced and that in itself can be very tedious indeed. Also, for the first while, as a beginner in flute repair you stab yourself with these little springs and it really hurts to put it mildly!
The pads also need to be taken care of and need to be replaced or reseated. They are made of felt and covered with 2 layers of fish bladder. I have no idea why they use fish bladder. Pads can get torn or punctured or just plain worn out. They are vital and cannot leak or the flute will lose some or all of it's volume.
Pad replacement is time consuming. Each ad is held in with a tiny screw and washer or a nylon snap. They vary in size and thickness. Once you have put them in you have to iron them and reseat them so that they will seal completely. To reseat them you have to wet them with alcohol and then clamp each key and pad, then heat them and if possible leave them overnight. It's not always possible to leave them overnight so I tend to put them in a pad oven and cook them for a couple of hours. This helps make the flute seal air tight when being played.
Next is to balance and regulate the keys with their newly seated pads.