The Flute Maker
A major advantage of working by hand is that keys and cup profiles can easily be altered to suit different tastes - people have very differently shaped fingers and it is good to be able to accommodate their habits! For example, the profile of an open hole cup is not as simple as it might seem: on most flutes the hole bells out slightly as it reaches the top surface and is surrounded by a raised ring which helps guide the finger into the correct position. This ring is often quite flat and badly defined, yet turns out to have a subliminal importance to a lot of players. This is after all the exact point at which a trembling finger makes contact with the flute so its correct position, shape and feel may be crucial to performance!
An old chestnut which probably concerns the repairman more than maker or player is the question of adjustment screws. These are the tiny screws used to regulate the synchronicity between fingered and non-fingered keys. Nearly all lower priced factory-made instruments have them, while most high quality flutes do not. It has to be said that when badly positioned they are an abomination: when placed too close to the key axis the slightest turn of the screw either way is geared up to a huge key movement making fine adjustment difficult and short-lived. Added to this they always have pointed ends which soon dig through the little cork or plastic buffers, leading to rattles. The alternative screwless clutch found on expensive instruments relies on the cork or felt interface remaining at constant thickness and the larger this is in area the better. But of course it does change with time and playing, so with no screw to turn, the repair person will usually add or subtract paper shims, a finicky trial and error process taking up valuable time. As an engineer I felt sure that a suitable screw could be designed and positioned for easy, fine adjustment which would not work loose and would not lead to rattles - most of my flutes have up to seven of these and they seem to work well.