Accurate sheet metal cutting

[KenLParticipant @kenl]

Posted by Kiwi Bloke on 24/06/2023 00:03:43:

The OP's application is for work finer than a Monodex (or similar) can produce. Actually, quite a challenging task.

Are you sure? Have you used one?

Back in the 1970s I did some very demanding work using one on thin stainless and brass sheet with good accuracy and nil distortion, The main requisite for good results is that the cutter plates are very sharp and carefully adjusted to suit the material being cut.

[Kiwi BlokeParticipant @kiwibloke62605]

Posted by KenL on 24/06/2023 11:16:49:

Posted by Kiwi Bloke on 24/06/2023 00:03:43:

The OP's application is for work finer than a Monodex (or similar) can produce. Actually, quite a challenging task.

Are you sure? Have you used one?

Back in the 1970s I did some very demanding work using one on thin stainless and brass sheet with good accuracy and nil distortion, The main requisite for good results is that the cutter plates are very sharp and carefully adjusted to suit the material being cut.

Yes, I've had a Monodex since the early 70s, and have enjoyed its use. Great tool, agree about the adjustment. The problems are the serrated 'blade' that leaves a serrated edge on the stock, and the need to cut very narrow parts. Some of these accordion reeds may be only 3mm or so wide, and need to be to accurate dimensions, with tight tolerances (a few thou on width – sorry about mixed units). Their sides are also stepped, being wider where the fixing rivet sits. So I think that, at least for DIY, they will need to be worked down to size. It's not an attractive prospect! If it's not a diatonic accordion, there are two reeds per note, and a full-size treble keyboard has 41 keys. There are also usually multiple banks of reeds. I think the OP is brave or misguided…

Edited By Kiwi Bloke on 24/06/2023 11:40:40

[HopperParticipant @hopper]

Seems like an ordinary straight bladed guillotine would do the job. Holds the stock clamped flat Cuts off a flat strip in one blow. Yes there is a small burr along the edge but that can be removed.

You want the proper gullotine where the straight blade comes straight down, hits the full length all at once. Not the shear type that has a scissor action that leaves a curled offcut.

[R Smith 1Participant @rsmith1]

Thanks folks.

"Do you really need to go down what can turn out to be a very deep and expensive rabbit hole?"

That's a funny question to ask on a model engineer's forum. The answer is, of course, yes, but it won't help me cut a square slot in the alloy, would it. You are right – way too much to learn for this particular task (although I've always wanted a milling machine).

I've come up with an acceptable process for sheet metal: cut strips with aviation snips, then define the base of the reed (the stepped bit where the rivet goes) with an eclipse nibbler tool. It cuts very well and almost without distortion, so only requires a light pass of a smooth file after it. Once the base is defined, the reed is cut roughly to width with sharp shears and then filed to size. I made half a dozen tongues this way without any problems.

"I think the OP is brave or misguided…"

No, just plain stupid

You are correct that in a factory setting, the reed is stamped. This is a controversial topic, as ideally, you want every reed to have its own size. Clicker stamping means that reeds are grouped into sizes to save money on dies, with same size serving up to half a dozen reeds. This reflects poorly on their acoustic properties, but factories don't care. E.g. I've got a Cagnoni a-mano (hand made) reeds in one of my boxes from 1980s, and they are still made from grouped blanks. This is supposed to be the creme de la creme of Italian reeds ffs!

The "real" hand made process, as employed by craftsmen in Neanderthal times is different. You size the slots. This doesn't have to have precise dimensions – at least not in model engineer's terms. The slots do need to have straight sides and the walls are angled slightly, so the "face" side slot is smaller than the other side. This stops the reed from clipping the frame as it passes. Interestingly, in a factory setting this is not done, the walls are stamped straight and the gap between the reed and the slot is increased. Another lazy, cost cutting measure.

The reed is then cut & filed to fit as well as possible in the slot – this is done by filing and this is where accuracy is required.

Then the reed is profiled & thicknessed, which is an art form the secrets of which are behind the seven seals and are passed from generation to generation of Italian and Russian reed makers… Of course, if you have a high quality hand-made reed block as an example, nobody's stopping you from copying it .

So far, I've had absolutely no problems copying half a dozen hand-made Cagnonis, which gives me hope that, as long as I can do the fitting and the riveting (I'm yet to try it when the right tools arrive), then the task can be done, and can be done better than a factory.

I play a CBA, and my biggest box has got 56 notes on the treble side and 52 in the (free) bass. 5 voices in trebles and 2 in the bass, two reeds per note, so there's 768 individual reeds in it.

Assuming I can, indeed, make an entire reed+plate combo, I'll be looking to downsize to only about 200 reeds, which should be very manageable. 4 reeds a week will only take me a year, and I'm in absolutely no rush, as this is just a fun wee project.

[MacolmParticipant @macolm]

A hobby bandsaw (eg Dewalt or Burgess, presumably neither still made!) fitted with a 24tpi or best a 32tpi blade can cut out fine detail without distortion. Cut the thin sheet metal held on top of 3mm or 6mm MDF for a clean edge. Depending on skill, accuracy can be good. Do final sizing by filing – clamp the work between two pieces of MDF in the vice with minimum projecting.

Another tool is here **LINK** and when new this cuts out fine notches without distortion. Unfortunately it is quite expensive nowadays, and only available in the USA.

[Colin HeseltineParticipant @colinheseltine48622]

I bought an old FJ Edwards 12" treadle guillotine a couple of years ago. It cuts all sizes of shim steel beautifully. I used engineers marking blue and then scribed line on it. It cut perfectly on the line, no distortion or bending of the material at all. I would look out for one of these.

Colin

[Colin HeseltineParticipant @colinheseltine48622]

There happens to be one on Ebay at this moment. eBay item number:394682584378

I have no connection to this advert, I juts did a quick search.

Colin

[HOWARDTParticipant @howardt]

Clamping the material between two steel bars and using them as guides to saw can result in a very clean cut. I have used this with a jig saw to cut thin stainless steel. It’s a simple cheap solution.

[duncan webster 1Participant @duncanwebster1]

This is probably irrelevant, but concertina reeds are parallel and held by a 2 bolt clamp. If you Google Kensington concertina they have a very good description

[Michael GilliganParticipant @michaelgilligan61133]

Probably not affordable for a short production run … but if you don’t ask, you will never know.

**LINK**

https://www.photofab.co.uk/our-services/photo-etching/

MichaelG.

[Andrew EntwistleParticipant @andrewentwistle]

i have used this approachable family firm for chemi-etching of stainless steel at work. Around £50 minimum order, but you can get quite a lot for that if you supply your own material and artwork;

Precision Photofabrication Developments Ltd

They are used to dealing with model engineers and can etch metals less than 0.05 mm thickness and also offer laser cutting.

Andrew.

[R Smith 1Participant @rsmith1]

Thanks for all the advice folks.

The PPD option is particularly interesting, especially that they are quite local-ish to me.

[Kiwi BlokeParticipant @kiwibloke62605]

R Smith 1 – I'm envious of your free-bass CBA. I'd like to learn B-system CBA, but the chance of getting such an 'exotic' beast here in NZ is tiny.

At a trade show, some years ago, I was given a small sample piece of stainless shim with intricate outlines and very narrow slots CNC laser-cut in it. Beautifully clean edges. I'll post a photo, if I can find it. I guess if that service is available in NZ, it will be available in more advanced countries…

Re my previous comments about milling machines. I don't wish to discourage you, if the desire is strong, but do be aware of the necessary expense and the need to learn quite a bit. I can't believe that many luthiers or accordion-makers have milling machines. After all that, when the machine is sitting idle, because it's easier and quicker to grab a file, just remind yourself that it really was money and effort well spent…

Edited By Kiwi Bloke on 27/06/2023 02:21:45

[R Smith 1Participant @rsmith1]

Well it's B-system, alright. But needs a lot of work done to it, that I intend to slowly carry out over the next year or even two (the only way I could afford the dang thing!). Not many repairs that are urgent, but all parts are starting to show their age and will need an overhaul sooner or later.

Getting B system in the UK is almost as bad. If your budget is unlimited, you can probably go for an AKKO or a Jupiter shipped to your doorstep. Otherwise, you're stuck hunting auction sites for old but very high end boxes from the Netherlands, sometimes Germany & Belgium, where B system was historically played. You only see about 2-4 a year that are worth buying and the price/condition is acceptable.

Grabbing a file is, indeed, better. I like hand tools and like learning to use then properly.

[Kiwi BlokeParticipant @kiwibloke62605]

Mentioning AKKO or Jupiter risks turning this thread into bayan porn… BTW, have you seen Ihor Pavlyk's YouTube videos?

Re reed manufacture. Take a look at **LINK**

John Cook, who seems to be the 'Great British Harmonica company', is a maker of harmonicas and works on other free reed instruments. His videos show the making of reeds from scratch, and the making of the punch tooling for it all. Impressive! Applicable to accordions…

[Simon Williams 3Participant @simonwilliams3]

Because we're a curious lot, I'm pretty certain that I'm not the only one who'd be interested to know what "A" system and "B" system infer.

An idiot's guide would be appreciated!

Rgds Simon

[R Smith 1Participant @rsmith1]

A CBA (Chromatic Button Accordion*) has got buttons on the treble side (unlike a piano accordion that has piano keys). Historically, the buttons have been arranged in 3 rows, with several layouts. B system, aka Do3 (B note in the first (outer) row), C System, with C in the first row (aka Do1). There are other, region – specific systems, like Do2 in parts of Belgium and Finnish C system. Since 3 rows are very hard to play, some clever guy decided to add 2 more rows to the keyboard, so that row 4 doubles row 1, and row 5 doubles row 2. This has made the C system easier and has revolutionised the B system, making it a lot more user-friendly than it used to be.

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

In essence, C system is typically associated with French musette, while B system with Eastern European music. Unless you are in Belgium or Netherlands, where B system is associated with musette music. Or in Germany, where B and C have existed side-by-side regardless of what music you were playing.

I hope this has cleared things up for you – the accordion is really, very straightforward. Until you open it up and see over 2,000 moving parts that all need to be set up to work perfectly.

*Do not confuse it with the British Chromatic Button accordion, which looks exactly the same, but is, in fact, a hybrid between a bisonoric 3-row melodeon and accordion-style Stradella bass, and is therefore not a chromatic button accordion, despite the name.

[Simon Williams 3Participant @simonwilliams3]

Fascinating, and thank you

Best rgds Simon

[R Smith 1Participant @rsmith1]

Kiwi Bloke – I've got a couple videos by a Russian melodeon maker on how to make reeds with just hand tools, the traditional way. And I've got some official measurements from a mid 2000s Tula bayan (including the bayan bass monsters!). Happy to share – just in case you're interested in trying your hand at it.

One week down the line I've made half a dozen sample reed tongues, including rough tuning, cut a few slots in a solid plank (freehand! I've been told that if I can't do this job freehand, then I don't know how to use a file, so I should learn it first, before I start using jigs to speed up the process), and fitted a reed to to a slot, much better than a soviet factory. Albeit, I still have quite a bit to go before I can match the Italian master craftsmen haha. All that with just a couple regular files.

I now need to make some safety files for the job, which might be a bit of a challenge.

I am yet to discover the dark art of using solid rivets, but overall, I'm quite happy, given that I've got close to zero metalworking experience.

[John HaineParticipant @johnhaine32865]

Aha! Electrochemical etching to make steel clock hands!

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