Mike - I dont have a mill to offer you  , although in the last week or so I bought 25 lbs of end mills for 75.00 - the going rate for what is left of one of the last oil field services in Oklahoma - $3.00 a lb - (yes not each- but per pound of end mills)it literally filled the bottom third of a 5 gallon bucket. Anyways on to my question to you - is that are you looking for an end mill in making your flutes ? - let me guess the true sound hole? - I used a method that required a router rather than an end mill - in all phases of the manufacture of the flutes that I made -I use the 2 piece of wood -method cut into square rectangular material - square as in the material would be the same width, height , and length and sqare to each other - I used a power jointer to achieve this  - the concept being that a core box bit would be used to make 1/2 of the cylinder , and true sound chamber on the top half of the flute ,  as well as the bottom is mirrored - and then joined and glued together. the importance of the 2 halves of the flute blank being square to each other  important in the next step of manufacuture - I would route the TSH channel - using a straight bit the appropriate diameter - 50/1000 proud - btw all of these operations I would use a router table - having flattened square stock mean that the 50/1000 for the 1 inch to 1.5 inch would be very uniform and centered - a pair of calipers is very important  to measue the depth - again the last step was to use a corner round router bit to do the outside of the flute to round it over - if done right I can leave the area around the TSH flat -I use sandpaper on a piece of thick plate glass as a flat surface and flatten the TSH are until I achieve the correct height of the TSH channel - I have not made a flute for a few years so I am not totally up to speed to how people are making them today - but for that matter I met a guy in Taos , New Mexico that did all of the same operations with a gouge and a horseshoe and xxxx files - I hope my long winded answer helps