The first thing you need to think about when making a flute is what type of wood you would like to use. This is an important consideration because the type of wood you choose will dictate the sound of the finished flute. You also need to keep in mind the tools you are going to use, hand tools or power tools. Softwood like pine or fir makes a mellower sound and is easy to work with hand tools, while hard woods like walnut have a sharper sound and is easier to construct with router. Out of all the flute I have made, fir is my #1 chooses for the sound.
To start, I use a ¾ inch thick piece about 24 inches long 1 ½ inch wide, unless I plan to carve a birds head on the end then I go with a 30 inch piece. If I am using a gouge to rough out the inside I like a wider piece of wood so I can carve both sides at the same time, usually 3 1/4” or a little wider works fine.
First I lay out the two chambers as you can see in the picture. The flute has a 1 inch ID and 1 3/8 OD. So I start by laying out a line ¼ inch from the edge, then I scribe a line 1 ¼ inch, this will give me a 1 inch inside chamber, Then I start removing the waste between the two lines. I use a gouge the scoop out wood in a half round shape to a ½ inch depth so that when the two pieces are glued together it will be a 1 inch round chamber, there is a ½ inch block about 7 ½ inches from the end and then another smaller chamber this section is the mouth piece. This is an air diverter that redirects the air out of a hole on the mouth piece side and then across another hole in the long chamber this is what makes the sound. Try to get the inside chamber as round as possible as you gouge the wood out. The sand it as smooth as you can this helps a lot with the sound.
Those who don’t want to do this project by hand can use a router with a 7/8 inch cove cutter to route out the two chambers, then you can go back and clean things up with a chisel. Be careful not to cut though the block. I normally do this on a router table.
When both sides are dished out and it is all smooth I like to drill my air holes and the scale holes. I drill the sound holes with a ¼ drill and the scale holes with a 3/16” drill. I do it this way so I can clean up any tear out. After the two sides are glued together I enlarge the sound holes with a round file to match the scale or in my case, what sounds good to me.