In article ,
James Waldby wrote:
Ken Cutt wrote:
Not exactly what you are asking and no where near as cool as CNC but ,
why not make up a reverse die and set that on the mag base , then just
use a regular surface grinder ? Luck

rashid111 wrote:
Ken -
do you mean use a pantograph style device to transfer dimension
of a die to the target ? Can you elaborate a bit here ?

I supposed he meant:
Cut out a cavity in a block, like a mold for the reed.
Put your stock in the cavity, hold both down via magnet,
and grind top surface flat (on ordinary surface grinder),
leaving proper cross-section.

With this approach, the hard parts are making the die
and getting the stock to hold down well enough. To see
if the process would work, I think you could make up a
quick-and-dirty die by a couple of cuts on a mill, with
a fairly arbitrary profile rather than an accurate one,
and take that die and some stock to a "shop or a friends'
grinder"

Hmm -- accordion (and concertina) reeds are very sensitive to
the contour of the bottom surface. Your method would be forcing the
flat bottom surface to curve to allow the removal of material from the
top side. When you release it, you may have a curve which will make
getting the reed to "speak" quickly (or at all) more difficult. I can
see you spending the time saved in the machining carefully bending the
reed back to the correct profile. (A curve near the tip will result in
a shift in pitch as the reed goes from a dead stop to a stable pitch --
and more of a shift with each increment in bellows pressure. There is
always some shift as a function of bellows pressure, but it is
beneficial to make that as small a shift as possible.

And aside from that -- at least some concertina reeds (I know --
the original question was about accordion reeds, but there are
similarities) will start out at a constant thickness where the reed is
clamped into the carrier, then a fairly sharp step, curving down to a
minimum thickness at about the 1/3 distance from the clamp to the tip,
and then gradually increasing in thickness towards the tip. I don't
know if any accordion reeds do this -- though I would expect it more of
the bass reeds on the left-hand end. Anyway -- such a shape would
require a rather massive magnetic field to achieve the initial
pull-down, and then a lot of work straightening the back when the
grinding is done.

And -- the contour of a reed may need to be changed from
instrument to instrument (as well as from note to note), so the number
of dies would quickly get out of hand, I fear. (Unless this is for
production -- the manufacturing of a single line of accordions, instead
of making replacement reeds for instruments from here and there.

Another consideration is that while the die and hold-down field
might work for the shape, it would still need quite a few passes of
gradually increasing depth to avoid burning the temper of the reeds with
the grinding heat (thus making the reeds duller and less responsive).

But -- it still might be an interesting experiment.

Enjoy,
DoN.

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