this is a set of questions for any DIY flute makers out there…
so, my understanding is that the wall of the embouchure furthest from your lips is generally shaped differently (in terms of undercutting) than the side closer to your lips. is this true?
also, is it possible to create a diy flute emb. that is undercut the same way on both of the aforementioned sides that actually sounds good?
finally–how does the cut of the “lip side” of the emb. affect the sound of the flute?
I’m very interested in making my own flute, as you can tell. 
Thanks, Mark
As far as I know, it really depends on the maker. My Copley flute seems to have the front (farthest) wall undercut a bit more than the back (closest) wall, and no cut on the sides (parallel with the flute). On my most recent PVC flutes, I’ve gotten the best response with a slight undercut all around (front, back, and sides), but with just the slightest more undercut on the front (a bit less than the Copley).
I’m not exactly sure what you are referring to here. Do you mean a cut like \ \ or still /\ ? Of course, those angles are a lot steeper in the illustration that it should be in real life (in my experience at least), but oh well.
It depends on the cut! There are way too many answers for this question! 
Oh well, to keep it simple (this is all from my experience, mind. I’m sure others will think a bit different), straight, flat walls with no undercut will often not have as much volume and not as good response as even a relatively poor quality undercut. Also, an undercut tends to give a slightly better sound quality. However, if you have too steep of an undercut, the flute will have a very covered and, in a way, soft sound (does that make sense?). This is probably because you are forced to blow at the top of the embouchure as opposed to the customary (in Irish playing) blowing down.
I do recommend making a LOT of flutes and experimenting this kind of thing for yourself as opposed to just taking my word for it. And know this (even though you’ve probably already figured this out), you can’t just make one flute. Once you start, you’re in it for good. Have fun! Oh, one more thing. When experimenting with embouchure cuts, you might try just making a couple flute bodies, and a bunch of heads that fit that body.
MeMyselfandI, I know that was alotta questions, and not alotta specifics. Thanks for answering anyway!
As far as Q #3 (How does the cut of the “lip side” of the emb. affect the sound of the flute?) I suppose i mean given a typically undercut front edge, what happens when you A: make the back edge undercut the same B: make the back edge U.C. steeper than the front edge C: make the back edge less steep. I wonder if there’s a known change in sound, or whether it’s just unpredictable and I should just expect to experiment alot. that sounds a bit like where this is going anyway.
RE: Q #2 i meant your choice “B” /_\ (understanding that the angles would be much less steep. I have read one maker mention a 7 degree angle. that’s not much.)
Thanks again!
well, never mind. I’m getting a Tipple. Decided it’s not worth the effort to make a flute because I don’t yet have the skills to play a good one, much less make one of quality. How could I possibly judge the quality of my own hack job? 
(no idea if that’s the appropriate emoticon, but I like it.)
ff
It’s hard describing how exactly to cut an embouchure hole. Well, it is for me anyhow. It helps to have a good working flute or two or three to examine. So get the Tipple and see what Doug does. I like Doug’s flutes. The larger holes on the newer ones work nicely.
Join the Yahoo Groups flutemakers group and read through the archived posts. There’s a lot there to absorb.
Search the archives here on C&F. There have been a couple very good threads on embouchure cutting. I haven’t found them quickly but they are here somewhere.
Google is your friend.
Have a look here. If you’ve never seen a blow hole it may help. They are not wooden flutes being described but the principles behind the Boehm style blow hole are the same.
Most of us start out emulating a hole on a flute we like. Then make a few head joints, test them, think, experiment and make some more.
Do you have experience playing flute? If not, sort that out on a known flute first. It’s not impossible to learn on a self-made flute but it’s sometimes leaving way too much up to chance. Edit: Looks like you already figured that out.
Not necessarily. Some makers make right handed flutes or left handed flutes with one side cut for sound production.. Some make ambidextrous flutes which sound from both sides.
Yes.
Hard to say but provided the close side of the hole is not done in a radical way it should not have a huge effect on the sound.
And have fun.
Feadoggie
thanks, Brother. I don’t see how I could fail at that!
Tipple should be arriving Wednesday. then the REAL fun will begin as I whip-train my lips to pucker in ways they may not want to!
HUZZAH!
Hi
I make flutes and I would like to know if I must round the inside edges of the embouche hole. I’ve tried several shapes but I cannot easily say what it changes to the sound. Currently I’ve just rounded the inner side edges, and a very little bit the front and back just not to left them sharp. It plays good but maybe it could be better ? ^^
As to answer to the author, undercut make the sound stronger and the flute more responsive, but don’t go too far because it weakens the first octave. I think big undercut = lighter tone, small undercut = more “reedy” tone.
I’ve heared that it also sharpens the second octave but I haven’t tried to confirm
My first flute was a home made one and I basically just undercut the far edge until it sounded good. I wound up with a pretty sharp edge. I don’t have anything to compare it to but it sounds pretty good. Maybe I just got lucky. Anyhow, I feel that if I could come up with a decent sounding flute without ever having seen a professional one it must be pretty easy to do a fair job of it. I would imagine it’s a lot harder to do a really good job consistently. Making your own is not very hard, doesn’t take much time, and is very fun. I would say go for it even with the professional one.
To nineflutes, the only edges of the embouchure that I would round are the top sides and back (so, all the top sides except the one you blow on). I wouldn’t round anything else (nothing on the inside edges, except maybe the sides), but do make sure it’s not rough, so make all the edges smooth. Rounding the top side edges helps reduce wind noise, rounding the back edge (closest to you) will make it more comfortable, but shouldn’t (as far as I know) affect the sound.
One thing to add to most of what has been said,be patient when making the embouchure hole! To make a really good embouchure hole, you will want to take off little by little with some small files, which can take seemingly forever, and can be very tedious. I used to just cut them with an exacto knife, which went well, but not as well as it could have.
To kokopelli, that story seems a lot like what happened to me! 
I started making them because I wanted to play flute, but couldn’t afford/justify one yet. So I started from scratch with next to no idea how flutes worked. It took me about 3/4 of a year to really get the hang it though. Course, I was mistakenly some Japanese Knotweed that I had in my back yard, which I thought was bamboo, but quickly learned otherwise (it was very very soft and fragile).
Knowledgeable flutemakers will know and could say vastly more, but I’ll chip in my observations from ~20 years of occasionally adjusting embouchure holes on old flutes, cheap bamboo flutes, delrin flutes, several Sweetheart flutes, etc.
Number one is…don’t try this with files. I have very small, very fine instrument files but it is practically impossible for me to produce a uniform undercut with a file. You are apt to work more in one area than another, and even if you move laterally, there’s an almost imperceptible rocking action going on. For me anyway. An X-Acto knife is better but much too thin. Ideal IMO is a very sharp but high-angle (~45 degree) pointed scraper. I modified the awl blade on an aluminum-sided Victorinox SAK for this purpose. It has to be very level and scrape very evenly and slowly without cutting any notches or grooves along the way. More gentle scraping than cutting, if you know what I mean.
You can finish up with extremely fine sandpaper wrapped around a rod or bamboo skewer. This is not shaping but simply smoothing things out, and don’t do much of it. In the course of that, if you very slightly round off a very sharp edge, I don’t think it harms the sound production and it reduces the risk of chipping. If you do too much, it hurts. That’s all I know how to explain.
Second is to have good magnification and lots of light from different directions. Try something like a halogen or LED gooseneck spot combined with a headlamp. And strong reading glasses or specialized magnifiers. A good embouchure is make or break and the differences are really tiny. It helps to have a good eye for tool angles.
Third but most critical of all is…patience. If you feel the tiniest bit like pushing forward and getting it over with, lay it aside and come back when you feel OK with this taking almost forever.
I haven’t seen hundreds of flutes, but those I have and have observed seem to have about the same degree of undercut on both the forward and back sides of the embouchure hole. I don’t know whether this matters.
I can confirm from experimental messing with some very cheap bamboo flutes (folks give me this sort of thing for some reason) that some undercut seems to make the flute speak easier and also eases the transition to the second register, but too much seems to rob the lower register of power. My impression anyway. Others will know more.
Good luck!
This brings to mind a story Casey Burns told me many years ago.
The very first Casey Burns flutes I played back then, when I met him at Lark Camp in the mid-1980s, played great, so he knew how to cut a good embouchure.
Anyhow he was saying that he cut his embouchures for right-handed fluteplayers and gave it no thought until he had a booth of his flutes out at some festival, and a guy picks up one of his flutes and starts playing it lefthanded! He said he hadn’t considered that before, and had to redo how he cut his embouchures.
BTW I’ve often wondered how it is that the inexpensive Ralph Sweet flutes have such a powerful Bottom D. I’ve wondered if it’s how he cuts his embouchures, the bore, or most likely a combination of the two. I’ve played very expensive flutes by other makers that, over the entire range, played much better than a Sweet but lacked the Sweet’s great Bottom D.