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[DaveCottrell]

Today, a colleague asked me about a repair on his bench.  It is a toy bugle with "valves" consisting of cylindrical tubes that contain brass reeds which look just like accordion reeds.  (Screwed onto a rectangular plate)

He needed to replace a broken reed tongue, so he fabricated a new one out of the same thickness brass stock.  He very carefully matched the original, and it spoke perfectly with no groaning or other issues.  However, it was almost an octave too low.  Which is when he called me.

I was stumped, thinking maybe the cylindrical chamber needed to be "tuned" like an organ pipe, because I could not imagine a reed of such similar construction being that far out of tune.

He later sent me an explanation of how he solved the issue.  He fabricated another reed out of .005" stock, while the original was .003"  (that's inches for the metric audience).  This solved the problem and he was able to replicate the original pitch without repositioning the reed in the chamber.

How does one explain the success of this repair?  Same reed plate, same reed shape, thicker reed tongue= considerably higher pitch.

[Tone Dumb Greg]

...How does one explain the success of this repair?  Same reed plate, same reed shape, thicker reed tongue= considerably higher pitch.

I suspect differences in the material properties.

[Theo]

It is rare for a reed to be the same thickness throughout it's length.  As a general guide the highest reeds are thinner towards the tip to get the pitch high enough, the lower pitches are thinned in the centre, and the lowest of all have additional weight added to the tip.

Thicker material is stiffer which will make the pitch higher, but thicker material is also heavier which makes the pitch lower.  Your friend was lucky in finding in getting the right pitch after only two attempts!

[pgroff]

I'm with Tone Dumb Greg and Theo.

Springiness / stiffness is important in brass reedtongues. Most brass stock that I see is not very stiff. When making brass reedtongues for concertinas, I follow the instructions I once read from a 19th century source, to hammer the brass blank, work-hardening it, before final fitting and tuning. Haven't had one break, and it results in a loud, springy reed (for brass) without needing to be too thick. Reed profile (thickness along the length) is also very important as Theo mentioned. I usually try to match that to another brass reed of similar length and pitch.

PG

[j.b.c.]

Springiness / stiffness is important in brass reedtongues. Most brass stock that I see is not very stiff.

A word of caution.

The add-alloy for spring-bronzes is Beryllium, a toxic and cancerous element.  BeCu makes wonderful springs, but don't go grinding on it and inhale the dust.

[malcolmbebb]

FWIW Colin Dipper work hardens brass for reeds by hammering it. And if it's good enough for him...

[IanD]

It is rare for a reed to be the same thickness throughout it's length.  As a general guide the highest reeds are thinner towards the tip to get the pitch high enough, the lower pitches are thinned in the centre, and the lowest of all have additional weight added to the tip.

Thicker material is stiffer which will make the pitch higher, but thicker material is also heavier which makes the pitch lower.  Your friend was lucky in finding in getting the right pitch after only two attempts!

If you double the thickness the mass doubles but the stiffness increases by 4x, so the pitch goes up half an octave [Freq=sqrt(Stiffness/Mass)].

[IanD]

Springiness / stiffness is important in brass reedtongues. Most brass stock that I see is not very stiff.

A word of caution.

The add-alloy for spring-bronzes is Beryllium, a toxic and cancerous element.  BeCu makes wonderful springs, but don't go grinding on it and inhale the dust.

But brass reeds are brass (copper plus zinc) not bronze (copper plus tin) beryllium-copper (copper plus a couple of percent beryllium) -- which is indeed nasty stuff if inhaled, though nothing compared to pure beryllium...

[pgroff]

It is rare for a reed to be the same thickness throughout it's length.  As a general guide the highest reeds are thinner towards the tip to get the pitch high enough, the lower pitches are thinned in the centre, and the lowest of all have additional weight added to the tip.

Thicker material is stiffer which will make the pitch higher, but thicker material is also heavier which makes the pitch lower.  Your friend was lucky in finding in getting the right pitch after only two attempts!

If you double the thickness the mass doubles but the stiffness increases by 4x, so the pitch goes up half an octave [Freq=sqrt(Stiffness/Mass)].

This is true if you don't change the properties of the material (crystal structure), but in my experience to use thicker brass, without hammering it, can yield a dull unresponsive reed even though it may come to your target pitch.

Possibly the original example worked well!  But possibly the correct pitch was achieved at the compromise of quick response.


So,  I'll reiterate the  point that I made above, based on a lot of experience making brass reeds - and as later restated by malcolmbebb (also above), referencing the Dippers:

the best way I've found to make a good brass reedtongue is to hammer the material - therefore, work-hardening it to increase springiness - before fitting, reducing (profiling), and fine-tuning.  This gives a springy responsive reed without excessive thickness.

PG

[j.b.c.]

brass (copper plus zinc)

Brass is the worst bronze.

[Broadland Boy]

@jbc  "Brass is the worst bronze." unless you were being ironic ( )

 You may have missed the point in Ian's second posting 

"But brass reeds are brass (copper plus zinc) not bronze (copper plus tin) beryllium-copper (copper plus a couple of percent beryllium)"

While there are varying grades of each, Brass and Bronze are two completely different alloys, as is beryllium-copper

Early makers pronouncing 'steel bronze reeds' on their boxes didn't help much either as those I've seen are brass !


@pgroff   peoples ability to hammer harden seems to vary, I've come across some quite accomplished clock repairers who just cannot master it, taking a bit of the required starting material to an amenable 'proper' jeweller, or at least one equipped with heavy duty rolls can produce a consistent and respectable compaction although probably not as hard as a decent hand peening.

[j.b.c.]

@jbc  "Brass is the worst bronze." unless you were being ironic ( )

I wasn't being ironic.

When I learnt metalugry in my far off youth the alloys of copper were referred to as *bronzes*

Copper has many alloys.  More than practically any other metal.

It doesn't make sense to talk about *brass* without specifying the specific alloy.  There are many proportions of zinc and other add-elements that change the property of the final metal.

It doesn't make sense to talk about metal sheet goods without specifying how they were finished.  ie hard, half-hard, drawn &c.

heavy duty rolls can produce a consistent and respectable compaction although probably not as hard as a decent hand peening.

A rolling mill is the right way to harden sheet.

A Sendzimir mill laughs at hammers.

[Winston Smith]

"A Sendzimir mill laughs at hammers."

Good point j.b.c., but I think that, as well as being too big for my cupboard, such a device might be more than my budget would allow when I need a brass reed replacing.

[j.b.c.]

I need a brass ...

An ideal source of quality coil-stock are the leftover ends from a production run of a fineblanking press (the kind of press that stamps out reed tongues), if you have that sort of industry in your area.  High value scrap!

[Theo]

My experience of making brass reed tongues is limited, but I have learned a couple of things that may be useful to others.
When I used brass I used hammering to harden it, but the hammering seemed to make little difference, the reeds worked well but cracked and broke quite quickly.
I then use phosphor bronze sold as “spring hard” and this worked perfectly.
I believe phosphor bronze was used in some better quality brass receded Whetstones from the early 20th century.

[pgroff]

My experience of making brass reed tongues is limited, but I have learned a couple of things that may be useful to others.
When I used brass I used hammering to harden it, but the hammering seemed to make little difference, the reeds worked well but cracked and broke quite quickly.
I then use phosphor bronze sold as “spring hard” and this worked perfectly.
I believe phosphor bronze was used in some better quality brass receded Whetstones from the early 20th century.

Really helpful, thanks Theo - great to know of a specific product that's available off-the-shelf, properly hardened for this purpose.

This fits with some earlier comments - I'm sure that rolling is a more consistent way to achieve work-hardened brass/bronze, compared to hammering.

Problems of brittleness/breakage from hammered reedblanks could be due to differences in the alloys used or the hammering technique. You want to develop just the right crystal structure / size / orientation in the alloy for springiness. There's a lot on the web about this.

 I got my brass stock years ago (and still have some left) as discarded scraps in various gauges from a machine shop and cut it into strips of varying width on a shear in that shop. Who knows what the alloy is, in my strips, but it's quite malleable and deformable. However, with only a small hammer and a  4" X 2" X 2" block of steel as an anvil I learned to harden these strips to yield blanks that can be filed into extremely functional, responsive, and sturdy brass reedtongues for concertinas - with some trial and error. I also practiced annealing them to soften again which can be done in the flame of a kitchen gas range (stove). This was useful when I made some brass accordion-strap brackets (those were out of round brass rod stock, bent, annealed at the bends, then hammered and drilled at each end).  To a certain extent you can go back and forth from soft to springy with brass, using heating/ annealing and work-hardening.  Quenching heated stock doesn't harden brass as it does with steel, but bending it will harden it locally in the region of the bend and hammering along the length will also harden it especially in that dimension. I may have gotten lucky with the alloy of my scraps, or maybe the many (wasted?) hours of experimenting can take the credit. But my guidance and the reason I had faith to try this was a popular magazine article from the 19th century explaining how to make replacement reedtongues, that was reprinted in one of the old Free Reed magazines (or the earlier Concertina Newsletter) - and then some advice along the way from my friend who had the machine shop and another friend who made jewelry and metal scupture.

Work-hardening can evidently go too far for reedtongues - there's a mention in another Concertina magazine article (about the history of the accordion industry in Germany) that harmonika reeds, as originally made by craftsmen who filed them by hand, sometimes developed too much work-hardening, thus the introduction of planing machines to profile the reeds to standardize the properties of the product.

I suspect that diatonix or some other melnetters who have studied accordion technology in great depth can tell us much more about this!

PG

[j.b.c.]

 I got my brass stock years ago (and still have some left) as discarded scraps in various gauges from a machine shop and cut it into strips of varying width on a shear in that shop. Who knows what the alloy is, in my strips, but it's quite malleable and deformable. However, with only a small hammer and a  4" X 2" X 2" block of steel as an anvil I learned to harden these strips to yield blanks that can be filed into extremely functional, responsive, and sturdy brass reedtongues for concertinas - with some trial and error. I also practiced annealing them to soften again which can be done in the flame of a kitchen gas range (stove). This was useful when I made some brass accordion-strap brackets (those were out of round brass rod stock, bent, annealed at the bends, then hammered and drilled at each end).  To a certain extent you can go back and forth from soft to springy with brass, using heating/ annealing and work-hardening.  Quenching heated stock doesn't harden brass as it does with steel, but bending it will harden it locally in the region of the bend and hammering along the length will also harden it especially in that dimension. I may have gotten lucky with the alloy of my scraps, or maybe the many (wasted?)

The vast majority of copper alloys are hot-short, meaning they become more brittle as you heat them, so you can't work them hot like you can iron.

You can look up the material properties of copper alloys here ==> https://alloys.copper.org/alloy/C26000

Metals producers datasheets specify the recommended usage, machinablitiy and forming process recommendations, and annealing temperatures and soak times.

[pgroff]

The vast majority of copper alloys are hot-short, meaning they become more brittle as you heat them, so you can't work them hot like you can iron.

You can look up the material properties of copper alloys here ==> https://alloys.copper.org/alloy/C26000

Metals producers datasheets specify the recommended usage, machinablitiy and forming process recommendations, and annealing temperatures and soak times.

Thanks j.b.c.

To clarify, I always hammered or bent brass in a cold state. I don't "work it like iron," because it's soft enough when cold to hammer or bend it.  However, that hammering or bending can over-harden the brass, making it brittle or likely to break. That's when annealing it came in handy. I did this in a gas flame, heating to red hot and quenching (since quenching hot brass doesn't harden it, it stays annealed).

I think you are suggesting that overheating the brass or overworking it when hot could cause damage to the crystal structure ? Interesting but I have never observed this. I know you can "burn" steel (i.e. the carbon in it) if you heat it too hot or long.  I never worked the brass when hot.

PG

[j.b.c.]

That's when annealing it came in handy. I did this in a gas flame, heating to red hot and quenching (since quenching hot brass doesn't harden it, it stays annealed).

I think you are suggesting that overheating ...

Just recommending that for best results one works to the materials properties.  Thermal treatment of metal requires care.

Cartridge brass (in the spec sheet I posted upthread) has a very low annealing temperature.  ~950F or 525C.

If you got it glowing red hot you've changed the alloy.

525C is a dull red, just barely visible in a darkened room.

https://en.wikipedia.org/wiki/Red_heat

[pgroff]

Thanks, totally agree that materials science has a lot to offer us!  I'm a scientist myself.

In 1989 when I learned to make good brass reeds, I was working in a 19th century way, inspired by 19th century information, with scavenged materials and the simplest tools in my 1 room apartment. And the instruments I was repairing were also 19th century.

Finally, my successful results* are evidence that this approach can work. And my experience I think is relevant to the original case in which a cheap toy was being repaired. The repairman had to go with thicker brass and my opinion is that he would have been better to match every dimension of the original reed, and hammer that thinner brass to a harder grain condition for more stiffness and springiness.

PG

* I have played a lot of great concertinas including Dippers and Jeffries, and can appropriately test the speed/responsiveness (when played both soft and loud),  durability, and timbre of a concertina reed.