Inside the NAF Flute

I build flutes that have bore sizes from as small as ½” all the way up to 1 ½”.  Typically I craft flutes with bore sizes of ½”, ¾”, ⅞”, 1”, 1 ¼” & 1 ½”.  The majority of the flutes we make fall into the ¾”,  ⅞” and 1” categories.  The larger the bore the bigger and longer your flute will be.  Most of the flutes made today have ⅞” and 1” bores as these are the most popular to work with.

The larger the bore the deeper the fundamental note or sound that the flute plays.  Some bore sizes will not make flutes in certain keys.  For example a 1” inch bore  works really good for a lower (maybe C#), D, D# and E.  Any higher or lower in the key range starts to be a bit difficult.  So you more than likely will not be able to make a great sounding flute in every key or range depending on the wood and bore sizes you select.  Below is a chart that can be used as a “GUIDE” that can help you choose select a target note for your fundamental note for your next flute.


Because NAF flutes play a single key you will more than likely end up with a collection of several bore sizes and lengths.  There is really no one bore size that is better than the other – it really depends on what your personal preferences are.  But if you are a beginner in building flutes I like to start people with a ⅞” bore and a 24” inch long blank.

Inside the NAF Flute

Ok so you have selected your flute blank wood stock.  We always start with two flute blank halves.  Both halves are identical and hopefully a matched set from the same piece of wood.  Your first step is to layout the flute so you know where the boring of the flute blanks will take place.  We do this by marking the flute blank with a pencil or pen and I will talk about each step.

When you are laying out your flute blank it is important to note that both the Blowhole and the Slow Air Chamber have NO effect on the tuning of your flute.  They do have an impact on the aesthetics of the flute and it will affect how long the total length of the flute is.  A proper length in your Blowhole and Slow Air Chamber are also important because the SAC acts as kind of an air bladder and a place for condensation from your breath to collect.  So here are our typical dimension for these two components.

Blow Hole – The diameter we use for almost every flute we make that have a flute bore diameter of ¾”, ⅞”, and 1” bores is ⅜” in diameter.  We use a ⅜” round over bit to create the blow-hole channel in each half of the flute.  You will essentially bore half the depth in each blank and when you glue the blanks together you will end up with a ⅜” diameter hole.  The length of the blow-hole again is up to you but we keep our blowholes between 2.5” and 3” inches long.

Slow Air Chamber – The diameter of this chamber will be whatever bore size you have selected.  So if you are making a ⅞” flute your SAC will also be ⅞” in diameter.  The length of the SAC can really be whatever you want it to be.  The longer the SAC the longer the overall length of your flute.  We typically make our SAC area the following length based on bore size:

  1. ¾” Bore – the SAC is 3” – 3.5” inches in length
  2. ⅞” Bore – the SAC is 3 ½”  – 3.75” inches in length
  3. 1” Bore – the SAC is 4” inches in length

Main Flute Sound Chamber – The longest portion of the flute blank that you will bore is the main flute bore chamber.  This is where all the sound is going to happen so make sure you are careful when boring this section of the flute.  You are going to run the flute bore from the front of the solid block area all the way through the end of the flute blank.

Next Step After Boring Flute Components


After you have completed crafting the inside components listed above you will need to create the exit hole coming out of the SAC and the inlet on the front edge of the Solid Block.  These two areas are critical that you do a good job when crafting these parts of your flute.  Especially the front edge of the block which is where your cutting edge (true sound hole) we be.  One of the advantages of crafting your flute from two blank halves is that you have the opportunity to work on the inside of the flute to not only sand and seal the inside of your flute, but you are given the opportunity to fine tune the exit hole and entrance hole into the main flute chamber.

If you look at the schematic drawing above (click to enlarge) you can see that we have a light blue shaded area on one half of the flute blank only.  This is the half of the flute where you will construct the Focusing Channel and Cutting Edge on the top portion of your flute.  I have found that it is important to craft a sort of ramp on the inside of the flute for both the exit hole leading from the SAC and a ramp on the inside of the cutting edge end.  I craft these two ramp areas with a very sharp gouge and I and very careful to blend the ramp into the two holes on both sides of the Solid Block.

I spend as much time as is needed to sand not only the bored areas of the flute but I pay special attention to these two ramps.  The goal is to create the smoothest path possible for your breath to follow, hopefully creating as little turbulence as possible when you play the flute.

We sand the inside of all parts of the blanks with at least 220 grit and then we seal the entire inside of the flute with Deft Sanding Sealer and then a Satin Finish follows.  I like the Deft products and we use their aerosol spray cans as they do a great job of sealing and they are easy to work with.  We put as many coats as needed in order to end up with a smooth finish throughout.  Be sure to mask off the gluing surfaces with Blue Tape prior to spraying any finish.

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