Sometimes students idly play with their headjoint crowns making them move the corks. Sometimes the corks dry out and move a bit on their own. Sometimes a tech has a new idea for a cork assembly and it dosen’t work out so well and the cork assembly moves.
The most common setting for a headjoint cork assembly for a C flute is 17.3mm. This means that the distance from the dead center of the embouchure hole to the plate of the headjoint cork assembly is 17.3mm. Almost all C flutes have the same bore size and basic shape of headjoint, making this adjustment nearly universal.
Swab sticks often have a line in them that is supposed to be 17.3mm. These swab sticks are often not made by the flute maker, but by a “job shop” where the machinist just sees a line on a drawing. They think it is just decorative and don’t bother taking the time to place this line correctly. Your trusted flute tech should have a tool that is spot on, and they can place your headjoint cork for you. Then you can use your swab stick to confirm that your line is in the correct place or not. If your swab stick is in the wrong place you could use a marker to give yourself a better located mark on your swab stick.
With Alto, Bass, and Piccolo instruments there is a much wider variety of bore sizes and shapes. Unfortunately this means that there is no one-size-fits-all measurement. Piccolo headjoint corks range from 8.0mm to 8.9mm depending on the manufacturer (and I wouldn’t be surprised if there were some outliers as well). Altos and Basses have a much wider range.
The cork should take at least a little bit of force to move. If it moves easily then take it to a repair person to replace the cork. If you want to remove the cork to inspect it keep in mind that all flute headjoints are a parabolic cone and the smaller part is the crown. Flute corks should be pushed down through the length of the headjoint and out the tenon side. It should not be pushed up through the crown side of the headjoint. Notable exception: Wood headjoints by Drelinger have a baffle that will not allow the cork to pass. He has opened up the crown side so that they go up through the crown end.
Piccolo headjoints are almost all cylindrical. They can be pushed up through the crown side. Notable exceptions: Nagahara Mini and some older metal Haynes piccolos that have a conical headjoint and a cylindrical body which are shaped like a flute, so that the cork assembly should be pushed through the tenon side like a flute.
If you don’t know where the cork should be placed there is a process you can go through to find the best place. This process works for any C flute/piccolo/alto/bass/contra. I recommend that this process be done by an experienced, advanced player of the flute/piccolo/bass/alto/contra in question. They will need to have experience with getting the different ranges of the instrument in tune in order to be able to make accurate judgments.
Tuning the Ds: How To Place A Headjoint Cork
1) Put the cork in the position you believe is best.
2) Use a tuner to tune the instrument with a nutral embouchure by moving the headjoint in and out, so that a note in the middle of the scale is dead on. I recommend F or G. F# will have an extra key down and we want to avoid that.
3) Once you are confident in the tuning of the F then tune the low D, the middle D and the high D with your embouchure. Note how far you are having to move to get each note in tune.
4) Pull off the headjoint and move the cork a fraction of a millimeter. For a piccolo if you move it about the width of the period at the end of this sentence you should be good. For a bass or contra bass flute, adjustments as big as 2 or 3 times the period at the end of the sentence will probably be fine.
5) Repeat steps 2-5 until you find the placement of the headjoint cork that gives you the least adjusting of the three Ds.
~ Erik Nugent