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[triskel]

A technique sometimes used by reed makers, accordion builders and harmonica fettlers is that of "coining", "chiseling", "stamping" (or "hammering") the reedframes, to reduce the gap between the reed tongue and the walls of its slot.

Hohner designer, accordion and harmonica technician, Rick Epping devised a method of burnishing the reed slots (later renamed "embossing") to reduce the gap around harmonica reeds, and later learned about the accordion "coining" technique (chiseling a line into the reedframe, parallel with the part of the slot you want to narrow).

He has written this about the embossing, or coining, of accordion reeds:

The main problem I can see in employing slot embossing on accordion reeds is that embossing effectively lowers the slot edge into the reed slot, creating a vertical gap between the reed and slot which requires the reed to be recessed into the slot at the rivet pad in order to compensate.  This is easy enough to do with harmonica reeds; factory workers sometimes use their fingernail to lower the reed at the rivet pad when adjusting newly riveted reeds and this how I adjust reeds after embossing.  Accordion reeds are thicker and much harder, being made of blue steel, and cannot easily be adjusted in this manner.  Coining an area of the reed plate offset from the reed slot can achieve similar results to embossing without lowering the reed slot edge.  I've attempted coining harmonica reed plates but found that they can become deformed enough to cause air leakage between the reed plate and comb.  Accordion reed plates are thicker and less likely to deform after coining and, anyway, are set onto their reed blocks with wax so that any irregularities or gaps between are filled.  However, I doubt that any technique like this was ever very widespread as I only ever saw it on a few old Hohner accordions, made during the period that the Italian master accordion maker Giovanni Gola was in charge of Hohner's accordion production.  My guess is that this was a technique that Gola had used in the past and for a period incorporated into Hohner accordion production. Accordion reed slots, even for high-quality handmade reeds, are stamped out on heavy presses.  After stamping, enough of the surface of the reed plate is then milled away to eliminate any material deformation around the tool entry area and create an even, sharp slot edge.

There was a discussion of the subject over on Concertina.net in October/November 2014: Hammering Reed Frames ?

I've especially noticed it used on reeds made by Harmononikas, in the Czech Republic.

[tirpous]

Something like this, you mean ? (these are bass reeds on an old 'H.S. Trade Mark' 2-row)

[triskel]

Something like this, you mean ? (these are bass reeds on an old 'H.S. Trade Mark' 2-row)

Yes, that's it done at the tips of those two reeds on the right, it can also be done along the sides.

There's an illustration on this page of the website of the Swiss accordion builder Reist too: http://www.reist-oergeli.ch/gestemmte-oergeli.html He uses it to "turbo" instruments! 

[pgroff]

Hi triskel,

I've corresponded with a Swiss friend who does this "coining" to improve reed performance, and I've often seen these chisel marks on Swiss instruments. Also have see it on occasional reeds in Paolo Soprani (and other good Italian) boxes from the 1920s and 1930s.

PG

[bellowpin]

Hi triskel,

I've corresponded with a Swiss friend who does this "coining" to improve reed performance, and I've often seen these chisel marks on Swiss instruments. Also have see it on occasional reeds in Paolo Soprani (and other good Italian) boxes from the 1920s and 1930s.

PG

   
a cold chisel in skilled hands of" reed maker" is one thing, but in the hands of a novice it could be a bit of a disaster!   looking at the image above ,I note how regular and precise the cuts are. 
     could there be some sort of press tool involved?    a chisel mounted in a drill press for example ,just a thought.   brian..   

[Winston Smith]

Please excuse my usual ignorance, but what is the actual hoped for benefit of narrowing reed gaps? Is it quicker starting, more volume, less air loss, deeper resonance/tone; what?

[Malcolm Clapp]

Please excuse my usual ignorance, but what is the actual hoped for benefit of narrowing reed gaps? Is it quicker starting, more volume, less air loss, deeper resonance/tone; what?

Less gap will enable the reed to be better set for quicker starting.
Not less air loss, but more efficient air use
Volume should benefit due to greater efficiency of the reed.
Deeper resonance and tone? Probably not, unless the pre-coining gap is extreme, in which case a replacement reedplate may be a better solution. There is a finite limit to the amount the gap can be closed successfully.

And a warning, though probably unnecessary: please don't try this while the reedplate is attached to the block as the force required is very likely to damage the block and to loosen the reedplate in the wax.

May I suggest trying this technique on, say, scrapped Chinese piano accordion reeds before risking damage to something worthwhile. They are notoriously badly fitting....