How far in should the tuning cork (is that what’s it called?) be in from the end of the flute?
Yup, it’s called the cork, the head joint cork.
The measurement you’re looking for is commonly measured between the face of the cork and the center of the embouchure hole.
On a Boehm flute, for instance, that distance is nominally set at 17 millimeters, while on a conical bore flute that distance could be 20 mm or so, depending on the flute.
The final test is in how well the flute responds, the goal being the most easily attainable octave leaps, etc.
Get thee to Terry McGee’s site…
http://www.mcgee-flutes.com/Stopper.html
Terry’s site has all kinds of interesting information (and his flutes are great, too)!
Pat
“Rule of thumb” is that the end of the cork should be the measure of the inner diameter of the headjoint back from the center of the embouchure hole.
–James
See my response at the end of this thread:
http://chiffboard.mati.ca/viewtopic.php?t=60057&highlight=cork
Kevin Krell
It shouldn’t be - you don’t/can’t measure it that way - see the other responses above. Different flutes (including modern Boehm ones) have varying amounts of “spare” tube above the embouchure, so there is no standard and you can’t usefully measure the stopper position from that end. Stopper assemblies and actual dimensions also vary, and the critical thing is the distance of the down-side face of the stopper from the centre of the embouchure.
Something that might work for you (once you’ve established the correct setting) is to measure the distance between the end of the cork and the cap on your headjoint (if you have one).
I cut a strip of cardboard to that width and about 6 inches long, then rolled it up and inserted the roll between cork and cap. (spiral visible from the cap end) It makes it very easy for me reposition the cork if it slips.
The formula for what peeplj spoke of is…
7 X (D/6) = distance from plugface to embouchure center.
Seven times the product of Diameter divided by 6 equals the distance for register balance. Mark the resulting measurement on your cleaning rod. Insert it into the bore and use it to push the plug up till the mark is located at the very center of the Embouchure hole.
Interesting formula, Thomas-Hastay - I haven’t come across that before. However, it poses some further questions. To what type(s) of flute is it applicable? - cylinder head/conoid body, or cylinder body/Boehm “parabolic” head, or both regardless? If the first, straight-forward enough, just use the head bore diameter (usually c 19mm). If the second, more complex - at what point in the tube is the relevant diameter? Is it that of the main body (viz 19mm in a standard Boehm flute) or is it that of the head at the centre of the embouchure or at some other longitudinal position? If it is one of the latter, it’s rather harder to determine what the diameter actually is!
If the diameter differs from the area of the embouchure to the area at the plug face, you must “average” these.
(D1 + D2)/2 = D avg
You can use the result as “D” in the formula 7 (D/6) = Distance. The same averaging formula can be used to determine bore diameter in a conical flute.
It really doesn’t matter how complicated a formula you use you still only get a starting point to begin experimenting with. If you cover more or less of the blow hole you’ll alter the optimal position of the cork a bit. And depending on the flute, and the type of music you play you may want to alter the position a bit. eg. on one flute I play I go up into the 3rd octave quite a lot so I need to set the cork to get the highest notes in tune. On another flute I play I don’t go up into the 3rd octave and the flute responds much better in the bottom octave (well bottom few notes actually) if the cork is at about 25mm. This drives the 3rd octave very flat but since I don’t play it up there it doesn’t matter.
So forget the formula. Start at about 1 bore diameter back from the center of the blow hole and experiment from there.
Cheers
Graeme
I have had good results placing the cork as follows:
Wait for a cloudless night with a full moon. Place the head of the flute on a flat surface such that the head end is pointing exactly due west. As the time approaches 9 PM (local solar time, not clock time), roll the head so the light from the moon shining thru the embouchure hole falls on the cork and/or inner bore of the head. At exactly 9 PM local solar time push the cork in until the light from the embouchure hole falls exactly 1/2 on the cork and 1/2 on the bore.
Then do what Graeme said, and adjust to suit.
Sorry, I couldn’t stop myself. 
The most dependable way I know to set the cork on a wooden flute is to adjust it until the low G and High G are at the same relative pitch with the headjoint all the way in. Unless something goes wrong with the cork itself (becoming loose or breaking), the cork should never need to be reset.