Tone Hole Leveling

Our finishers spend quite a bit of time padding flutes -- making sure that the pads are flat, shimmed, and level in the keys.  However, if the tone hole crown (top of the tone hole) is not level, all of that hard work would go to waste!  So, one of the most important steps in the finishing process is leveling the tone holes.  This process is done with both drawn and soldered tone holes. 

As with many steps in the finishing process, each finisher will have his/her variation on technique, but Karl Kornfeld demonstrated the process to us recently.  He first takes a magic marker to mark completely around the top of the tone hole.  Karl uses a green marker, although he said that any color would work.  He prefers not to use blue since the protective tape used on the flute is blue.  He then takes a small piece of a flat file and wraps it with a piece of 1200 grit sandpaper.  The flat file provides a flat surface for the sandpaper to work with in the process.  He then takes the wrapped flat file and gently sands the tone hole crown until the green marker ring disappears.  Karl shared, "If it's done correctly, it looks like a silver ring that is glowing green."  Glowing?  Well, in other words, because the tip of the magic marker is wider than the tone hole crown, a bit of marker will remain inside the tone hole -- which gives the "glow" after the green marker on the crown is sanded down.  After sanding the crown, if it looks like the silver ring is not complete (spots of green still visible on the crown), that means that there may be a low spot.  In this case, the crown must be leveled a bit more to make it flat.  Karl said that the lowest spot on the tone hole crown determines how much leveling needs to be done. 

Obviously, all this hand work takes extreme care and expertise.  The exact amount of pressure to use and actual technique comes from much practice.  As Karl mentioned, this process is extremely critical for seating pads properly -- and for making sure the entire flute mechanism fits and functions as it should as well!

Marking the tone hole crown.

Crowns marked all the way around.

Flat file

Flat file wrapped in 1200 grit sandpaper.

Leveling the tone hole crown by sanding.

Green ring gone (silver ring "glowing green" now).

Green marker left on this ring shows a low spots.

Hand Shaped Corks

You've probably heard the term "hand shaped corks," but what does that mean?  Are these corks on your flute really shaped by hand?  Well, the answer is yes!  We recently caught up with flute finisher Karl Kornfeld to take a look at the process.

Corks are used on the trill keys, G# key, and D# key.  Powell receives a supply of corks in the shape of small "barrel-type" pieces -- similar to a cork from a wine bottle.  One cork piece will be used for the 4 keys mentioned above.  The cork is first cut into quarters.  Karl prefers to take one of the quarters and then cut that quarter in half for the trill keys.  This helps with consistency and allows for these corks to (aesthetically) "match."  When we caught up with Karl, he was working on a D# cork.  For this key, he uses one of the cork "quarters."  He uses contact cement on one side of the cork and the back of the key.  Then, he presses the two together and holds them (with the help of some equipment) until the glue is dry (about 10 seconds).

Now the shaping process begins.  The cork must be shaped so that the key opens to a standard measurement that Powell uses on their flutes.  A cup height gauge is used to periodically check the height of the key cup opening as the cork is shaped.  Finishers use a combination of double-sided razor blades and various grits of sandpaper (220, 400, 800).  The higher the grit, the finer the sandpaper.  Karl puts the key mechanism back on the flute and marks the cork in the center, where the cork touches the center of the "box" (box is the area between the sides of the ring).  He then begins to shape the cork with the combination of sandpaper and razor blades.  In the photos below, the thin strip of sandpaper is 220 grit, and the larger piece is 400.  The 800 grit is used for very fine adjustments.  He continues sanding and shaping the cork until it is the correct size and shape for the key to open properly at the calculated height -- which is critical. 

There are other mechanisms which have cork for adjustments, and for these, small slices of the original cork are used.  So, now if you hear the term "hand shaped corks" with Powell flutes, you'll know that they are truly hand shaped by our finishers!

It begins with a piece of cork.

Cork piece divided into quarters.

One quarter piece for the D# key.

Applying contact cement to cork (and then key).

Pressing key and cork together.

Holding key and cork together until glue dries.  Leather strip is used to protect key.

Shaping cork with razor.

Marking center of cork where it meets center of the "box."

Sides of cork should not touch sides of ring.

Some shaping with a 220 grit strip of sandpaper.

Checking key opening with cup height gauge.

More shaping with a 400 grit piece of sandpaper.

Finished!

Quarter cut in half to match trill key corks.

Slice of this piece used for adjustment cork.

The Bamboo Flute

Verne Q. Powell was a man of exquisite talent and ingenuity when it came to building flutes.  We've seen the craftsmanship of instruments he built from precious metals and wood, but there is one particular flute here at the Powell facility that is quite unique -- the bamboo flute. We recently found more information on this flute in our historical archives:

The "Bamboo Flute," Powell number 392,  is a Boehm Flute made in 1940 of a Bamboo walking stick that Mr. Willis J. Abbott brought to Mr. Powell on a trip back from China.  Mr. Powell then turned the walking stick in to a flute and gave it to his good friend William F. McKenzie. The flute is pitched in D and features engravings of monkeys along the back (see photo detail).  The top of the headjoint has a silver cap, which is engraved with the following:

“Friendship Flute

Made for

William F. McKenzie

From a Chinese Cane

The Gift of

Willis J. Abbott

Verne Q. Powell

Boston

1940”

Undercutting Tone Holes

You may have heard the term "undercut tone holes" or have read about "undercutting tone holes," but what exactly does that mean?  We spoke with flute finisher Karl Kornfeld and repair technician Rachel Baker about undercutting.  Rachel shared with us that undercutting tone holes is something that is fairly recent.  Both soldered and drawn tone holes can be undercut, although soldered tone holes would tend to have more undercutting.  Why is this?  Well, essentially, with soldered tone holes, a hole is cut into the flute body, and then then "tone hole" is soldered onto the body with the inside edges of the hole flush with the actual hole in the body.  Because the tone hole is soldered straight down onto the body, there could be sharp edges where the tone hole meets the body.  These sharp edges can cause turbulence inside the body and need to be rounded.  The rounding of these edges is what is known as "undercutting."  Less undercutting is needed on drawn tone hole flutes because the tone hole is formed by pulling metal up from the body.  Because the metal is not pulled exactly in a straight line, there is already a bit of rounding on drawn tone holes.

Undercutting is an extremely delicate step that takes care and precision.  If there is not enough undercutting, the player might feel more resistance when playing.  If there is too much undercutting, you can lose focus in the sound and definition between notes.  As Rachel reminded us, as air travels through the flute, there still need to be nodal points for the air as it travels.  Too much undercutting can disturb the air flow.  We've included some photos of two tone holes on a drawn tone hole flute.  One hole has been undercut, and the other has not yet been undercut.  It's difficult to see, but the undercut tone hole has a bit more of a reflection on the edge of the hole in the body.  The other tone hole is a bit more "'dull" around the edge.  Coincidentally, we caught up with a former Powell flute finisher who is now working on saxophones with soldered tone holes.  The tone holes are soldered with the same process that Powell uses on its soldered tone hole flutes.  Because the saxophone tone holes are so much bigger, it's much easier to see from that photo the difference between the undercut tone hole (smooth around the edge) and the one that has not yet been undercut (rough around the edge).

Many older flutes do not have undercut tone holes, so if yours does not, it's okay.  There are many types of flutes for many types of flute players!  If you have additional questions, always remember contact your authorized repair technician.

Red arrow points to undercut tone hole, orange to tone hole that has not been undercut yet.

Close-up of tone holes (top, undercut and bottom, not undercut)

You can really see the difference with these soldered saxophone tone holes.  Red arrow points to undercut.  Orange arrow point tone hole yet to be undercut (you can really see the rough edge).