Making the Embouchure
Some builders make the hole in one shot by drilling a hole on an angle. I find that this tends of cause more trouble than it is worth for me, so I use a straight hole then shape it afterwards with needle files to its final shape. The most important part of the hole is the blown edge on the opposite side of the flute from the player. This edge should stay as sharp as possible. To get the right angle on the blown edge, I use the needle file to carefully undercut the hole. I start on the interior edge of the pipe where the most material will need to be removed with the needle file held at the angle Iím shooting for. I continue to work the angle back until the entire edge is uniform and cleanly cut.
Start with about 45 degrees between the outer and inner edges. Depending on the size of the tubing compared with the diameter of the embouchure hole, it may not take much to reach the right angle, but it is critical to getting the most out of the flute. More filing is needed on larger pipes and on smaller embouchure holes to get to the correct angle. It may be easiest to go ahead and finish the rest of the instrument so it is playable, and then tweak the blown edge until you can get the best tone and control. But donít get greedy: you can always take off more material later but you canít put more on.