Aerodynamics 101. Without "undercutting", the airflow will go from more laminar to more turbulent as soon as it passes over the 90 degree angle from the bore to the tone hole (think river eddy). In mechanical engineering terms, "Undercutting" is a chamfer, which allows the airflow to remain laminar longer, which allows the air to move faster through the tone hole, changing the pitch. Chamfering the entrance to the tone hole simply changes the point at, or extent to, which the airflow becomes turbulent. Polycylindrical bores are another attempt to manipulate the fluid dynamics of the airflow in a favorable way.
I sped this up to 1.75 And it was still tedious. The content: Undercutting raises the fundamental more than the 12th, it increases flexibility and « freeness » of a note. It can ruin an instrument if applied unreasonably. Repeat that 100 x’s over in a very slow dragging voice.
Excellent video and have been waiting for a vid on undercutting, so thank you Tom!! A couple of questions: are there different kinds of undercutting reamers? Are they all straight angled or are some reamers designed to give a curved undercut? I suppose I should have prefaced that last question with: does the shape of the undercut make a difference? Would undercutting work just as well on an ebonite or "plastic" clarinet as it would on a wooden clarinet given the same problems that it's designed to solve.
Excellent questions. Yes, there are different sized and tapered under cutters. The less extreme the angle the further the undercutting will go into the tone hole. The more extreme the shallower the under cutter will rise into the tone hole chimney to remove the same amount of material. Less extreme angled under cutters correct tuning issues and maximize the resistance change as well. The great angle under cutter adjust tuning but affect resistance somewhat less. There are curved or radiused under cutters, both convex and concave. No concave under cutters I know of are used on the clarinet. Only one convex under cutter is used in limited cases.
Aerodynamics 101. Without "undercutting", the airflow will go from more laminar to more turbulent as soon as it passes over the 90 degree angle from the bore to the tone hole (think river eddy). In mechanical engineering terms, "Undercutting" is a chamfer, which allows the airflow to remain laminar longer, which allows the air to move faster through the tone hole, changing the pitch. Chamfering the entrance to the tone hole simply changes the point at, or extent to, which the airflow becomes turbulent. Polycylindrical bores are another attempt to manipulate the fluid dynamics of the airflow in a favorable way.
I sped this up to 1.75 And it was still tedious. The content: Undercutting raises the fundamental more than the 12th, it increases flexibility and « freeness » of a note. It can ruin an instrument if applied unreasonably. Repeat that 100 x’s over in a very slow dragging voice.
What about bass clarinets???
Of course, if one were able to radius that transition, you would get a better result (faster airflow) while removing less material.
Excellent video and have been waiting for a vid on undercutting, so thank you Tom!! A couple of questions: are there different kinds of undercutting reamers? Are they all straight angled or are some reamers designed to give a curved undercut? I suppose I should have prefaced that last question with: does the shape of the undercut make a difference?
Would undercutting work just as well on an ebonite or "plastic" clarinet as it would on a wooden clarinet given the same problems that it's designed to solve.
Excellent questions. Yes, there are different sized and tapered under cutters. The less extreme the angle the further the undercutting will go into the tone hole. The more extreme the shallower the under cutter will rise into the tone hole chimney to remove the same amount of material. Less extreme angled under cutters correct tuning issues and maximize the resistance change as well. The great angle under cutter adjust tuning but affect resistance somewhat less.
There are curved or radiused under cutters, both convex and concave. No concave under cutters I know of are used on the clarinet. Only one convex under cutter is used in limited cases.