Klarinet Archive - Posting 000039.txt from 2007/08

From: "Clark W Fobes" <claroneman@-----.net>
Subj: [kl] Machining wood
Date: Thu, 09 Aug 2007 11:28:03 -0400

Hi Tom,

I will try to respond to most of your questions.

There is no doubt that some heat is generated when machining wood, but
the greatest amount is created when the blank is initially through bored. I
use a very sharp, 0.5" drill bit for the initial bore and it generates a lot
of surface friction. The less wood that has to be removed the less heat is
generated and we experience the least amount of change. This is why I pre
bore the tenons to just under the final dimension.

Depending on how green the wood may be, we can see the wood "sweat" as
the drill bit pierces the blank. It has become very clear to me that African
Blackwood is naturally very wet. The wood I am working through now was
bought from Theodore Nagel in 2005 and they said it had been on the shelf at
least 10 years. We still see the material sweat as we work on it, but it
dries quite well once the blank is through bored. I think your point that
clarinets must be machined over several days if not weeks is well taken.

As to wood actually "smoking" when it is machined, I have never had this
experience with African Blackwood. I did observe that once with Cocobolo,
but I was experimenting with a tool that was obviously not right for the
job. Smoke would indicate that a tool was very dull or being forced too
quickly through the wood. African Blackwood is notoriously hard on tools and
the bits must be changed when they begin to get dull. When a cutting bit
becomes very dull it slows down the process immensely and the cuts are not
as clean.

Tool chatter (which causes roughness or patterned surfaces) is another
matter. The position of the bit in relationship to the surface and the angle
of the bit are critical to a clean cut. If the tool is positioned
incorrectly it will tear the grain rather than cut. It may also chatter. But
this should be apparent with the first few cuts and any decent machinist
would recognize the problem and reposition the bit before proceeding.

I have seen some custom made barrels that have a "scalloped" bore. This
is caused by the reamer. If you are reaming a barrel by hand (the only way
you can really control the dimensions) you must have a special wood cutting
reamer. Not only are the flutes sharpened differently than from a high speed
reamer, but the flutes (if it is not a spiral flute reamer) must be offset
from each other by a few degrees. If the flutes are evenly spaced the tool
will chatter and create an uneven or "scalloped" surface. I also know that
some makers prefer to make the final bore of their barrels with the lathe
and a boring bar, but the bore lacks a smooth finish. Hand reaming also
allows me to play test and adjust the barrels in a few minutes.

I am working on a set of photographs of the entire process we use in
making the barrels and at some point I hope to have a slide show of the
process on my website.

Clark

Clark W Fobes - Clarinet & Saxophone products
www.clarkwfobes.com

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