The thumb key on the flute is a notorious trouble spot. As the highest tonehole on the flute (discounting the trill and small C# toneholes), the thumb, or C tonehole is critical to the proper functioning of the rest of the instrument. If there is a leak in the C tonehole, every note below it is affected.

Unfortunately, the key mechanism covering this tonehole is especially prone to wear, due to the short length of the mechanism tubing involved, and the action of the player's thumb at right angle to the key's axis of rotation. Also, as the soft silver mechanism tubing is supported by a hardened steel shaft, the key will wear and develop play.

Every year we receive requests from players of other flutes to re-cut their headjoint. The response of their flute has worsened and they believe the problem lies with the headjoint. Often the problem is found be the result of play that has developed in the thumb key mechanism, causing the C tonehole to not close properly. The solution is Nagahara Patent 5,708,226.  A drawing this special double-sleeve design shown below.

 

Thumb Key