Caring for Your Headjoint
Make sure that your headjoint fits your flute properly. A fit that is too loose will result in a weak sound, just as if pads are leaking! Keep the inside of the barrel clean, and also the headjoint tenon. Accumulated dirt can damage them. Nail polish remover is very good for removing gummy or sticky dirt; use in a well-ventilated area.
Please be careful when wearing jewelry, especially rings. Any metal-on-metal contact will leave a mark. A scratch or nick too near the engraving or on the tube around the lip plate is not usually repairable. A dent or scratch on the embouchure hole, especially the blowing edge, may damage the headjoint beyond the point of restoration. A tiny nick in the blowing edge can cause the headjoint to play in an unfocused manner. Be careful about wearing anything metallic while handling a flute. Jewelry, belt buckles, microphones; even orthodontic braces can mar the headjoint.
Check the headjoint cork position. The line around the end of your swab stick should measure 17.3 mm or 0.681" from the end. Place that end of the swab stick into the headjoint, with the stick touching the stopper. Look at the embouchure hole, and observe where the line seems to be located. It should appear to be in the center. Now turn the headjoint around 180˚ and look again. Is the line still in the center of the hole? Sometimes it gives the illusion of not being centered when observed from both directions. In that case, the cork should be placed to make the line appear off-center by the same amount when observed from both directions.
A headjoint cork should not be loose but should be moveable with concentrated effort and care. To move the cork toward the embouchure hole, unscrew the crown a turn or two, leaving a space between the crown and the headjoint tube. Push the crown toward the tube. When the space disappears, you know that the cork has moved. Check its position with the swab stick. To move the cork away from the embouchure hole, tighten the crown and check the alignment with the swab stick to see if the cork has moved. The threaded rod positioned in the center of the cork will "climb" the threads inside the crown and pull it up. If you cannot get the cork to move this way, try to push the cork (be gentle!) from the inside with the blunt end of a wooden swab stick. Never force a cork assembly toward the crown end of the tube. Severe damage may occur to the headjoint if the cork assembly is forced too far up the tube.
Take care in choosing your flute and headjoint. They not only represent a financial commitment, but an artistic one. A little care and diligence in the maintenance of your instrument will keep your flute and headjoint in good condition for a long time.