Author: cjwright
Date: 2010-07-01 17:24
Usually when people measure "the sides" they check just below the ears of a piece of shaped cane. Naturally, depending on the shaper, every person might have different measurements for a piece of cane that is gouged on the same machine.
In order to find out whether you have a double radius or a single radius is to look at it and see if the bed can be offset, often times by screws on the bottom of the machine. Pull back the clips and check to see if your blade is straight down the middle of the bed or if it's offset somehow.
Not sure what your gouge is but .05 is pretty darn small difference, and implies that your channels are pretty thick, and your rails/sides must be very very thick. Back in Tabuteau's day, they used .60 in the middle and .40 on the sides. Mack used closer to .60 and .45, and a bit thicker later down the line. Today, most people use around .60 and .45 to .50 on the sides,
If your gouging machine is a single radius, you will want the curvature of the blade to be approximately the same shape as your guide, except the entire blade is a hair bigger. Your curvature should be almost exactly circular, and not elliptical. So if your guide is 10.5mm diameter, your blade should be closer to 11mm or 11.5mm diameter. It's important that the blade curvature match the guide or else your chips will cut unevenly and you will have an imbalance of push to pull forces (the blade pulls the chip up, the guide pushes the cane down into the bed, etc.)
If your gouging machine is a double radius, you will want the curvature of the blade to be similar to the guide as well, however, the blade diameter needs to be smaller (9.5 or so on a 10.5 guide), however your blade should be more elliptical. As to the "exact ideal elliptical shape", that's a mystery, and what people commonly refer to as "the holy grail of gouges". There's no way of knowing exactly, and therefore you just have to do trial and error.
In any case, the way to find a "working" curve is simple. Make two or three reeds, each from a piece of cane that has roughly the same diameter, and after all of the refining, if you still find that it sags in the upper register, make the sides thicker (if you have a double radius machine) or regrind the curve to a smaller diameter (if you have a single radius). If the three reeds come out open, "hard sounding", and glassy, thin the sides (w/double radius) to get a warmer sound or regrind the curve to a bigger diameter (for a single radius).
One final warning, if you have a single radius machine, come up with a system to make sure your blade is exactly in the center, or else all of your work will be for naught.
Cooper
Blog, An Oboe In Paradise
Solo Oboe, Thailand Philharmonic Orchestra
Post Edited (2010-07-01 21:25)
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