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After facing
and center drilling, I drilled a 5/8" hole that is the opening
in the cap. |
After drilling the cap hole, I have stabilized the ivory with the
live center and I'm turning the diameter down to 1-7/8", the
size of the bass drone cap. |

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After removing the live center, I'm hollowing out the underside of
the cap by 3/8". With a 1/2" finished thickness, this will
leave a top 1/8" thick.
I made one this size for the bass drone. Then I turned the cylinder
down to 1-3/4" for the two tenor drone caps. They were turned
the same way. |
Here are the three cap blanks finished to this stage. Their finished
profiles will be turned after epoxying them to the blackwood. Finish
turning will reveal the lip around the center hole and the protruding
rim at the base. |

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This shows drilling the center again. This time it is a 1"
diameter bit for the ferrules.
Imitation ivory must be turned relatively slowly. Faster than 500 rpm
and it is likely to shatter. It also form best with a negative rake
tool. The excess material is scraped off instead of slicing it off as
a positive rake would do. |
After center drilling, I'm turning the diameter down to 1-1/2". |

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Here the parting tool is starting the cut to trim off a ferrule blank
from the drilled rod. The rod is spinning in my lightly held fingers
to catch it when it parts from the rod. |
Here the ferrule blank has just parted and fallen off in my hand. |

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Here are the completed mount blanks. The three on the left are for
the bass drone and the 4 on the right are for the tenor drones. |
This shot shows a billet in the 4 jaw chuck being center drilled to
accept a live center.
Just like the lower drone section, the next steps are to turn a land
for the follow rest, gundrill the bore to 9/16", re-chuck on the
bore, rough turn the external diameters, and finish turn the final
profile. Since those steps were shown in the lower section, I skipped
them here. |

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This shows one of my more "creative" tool set ups. The boss
for the ferrule is held in the three jaw chuck. The follow rest is
installed on the lathe apron and the tool holder is holding a roller
bearing to firmly hold the rotating work piece. This left me without
a tool holder. I clamped a piece of inverted angle iron in the side
of the indexing tool holder to act as a rest for a hand scraper.
Please don't show this setup to a real machinist. I'll loose bragging rights! |
This is a little closer. I used a 7/8" drill to start a hole in
the end. This is the diameter of the bell at the end of the drone section |

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Here you can see me working the scraper inside the bell to shape it.
This is the only "done by feel part of the operation. The bell
is 1" deep and completely blind to cut. |
Now you can see the finished bell profile. This phase of the bore
shaping is the most variable and my account for the biggest
differences between examples of the same brand of pipes. Without
modern machinery and custom cutters, it is impossible to make the
bell shape exact between individual pipes.
I tried to follow a generally parabolic curve in turning the bell profile.
The bell profile and depth, the bore diameter relationships, and the
location and length of the tone chamber, all come into play in
shaping the sound. These will be the variables I'll play with in
changing the drone sound.
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Here is a shot of the completed tenor drone sections, sanded and
oiled along side a 1:1 scale print out of my model. In a week or so,
after the oil cures, I apply a coat or two of shellac.
I modeled the drone parts in Rhino, a Windows based NURBS modeler and
checked the model against the x-ray images Dr. Jack sent me.
I used this model to check dimensions and locations as I made the
parts along the way.
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