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questions about making tongues


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Paul, thanks for your helpful measurements.  

 

Alex, thanks for your detailed explanation.  I calculate that the average spread in all of Paul's measurement to be 0.0059 inch, or +/- 0.003 inch.  Can you estimate the average gap between tongue and slot that you get with your finished product?  

 

If I recall correctly, Dana once commented that his gaps are maximum about a half thousandths of an inch.  

 

Paul's measurements indicate that the slot inaccuracies don't follow the same trends among the different results, and that would perhaps make filing the tongue more tedious.  I'm curious how you visualize the gap in order to see  how your filing is going.  I once used an optical comparator, which, on an overhead screen, displayed a very magnified version (10x) of whatever you placed on the table, which had a glass surface that was backlit.  I'd think that such an apparatus could be very helpful for this kind of work.  

 

Regards,

Tom

 

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1 hour ago, ttonon said:

Alex, thanks for your detailed explanation.  I calculate that the average spread in all of Paul's measurement to be 0.0059 inch, or +/- 0.003 inch.  Can you estimate the average gap between tongue and slot that you get with your finished product?  

 

If I recall correctly, Dana once commented that his gaps are maximum about a half thousandths of an inch.  

 

Paul's measurements indicate that the slot inaccuracies don't follow the same trends among the different results, and that would perhaps make filing the tongue more tedious.  I'm curious how you visualize the gap in order to see  how your filing is going.  I once used an optical comparator, which, on an overhead screen, displayed a very magnified version (10x) of whatever you placed on the table, which had a glass surface that was backlit.  I'd think that such an apparatus could be very helpful for this kind of work.  

 

I don't have a good way of measuring it. Certainly less than 1 thou. I used to use a low power optical binocular microscope, but I've lately switched to a 1080p video microscope connected to a 22" monitor. I place the reed assembly on top of a lit stage to illuminate the gap.

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10 hours ago, lucayala said:

hello again. there are some suppliers that sell 1095 tempered steel in rolled strips like this:fleje.jpeg.dac304f2183f09fb1f057255b6a722e6.jpeg

would this work? I understand that if it works I should straighten the steel somehow

 

Can you get them to give/sell you a small sample that you can try first? A few years ago I bought a 10Kg roll of spring steel from a new supplier, cut 50mm off the end, and made a couple of test reeds from it. It was no good: much too soft. The supplier refused to take it back for a refund because I'd cut some off it. Expensive mistake.

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39 minutes ago, lucayala said:

oh, that's bad. I will try to get some samples

how did you straighten the steel?

 

It will probably already be reasonably straight once you've unrolled it. Beware it is likely to instantly and violently unroll itself if you simply cut the band that holds it together (and to make matters worse it may have razor sharp burrs on the edges). Once you've cut a piece off the roll and sheared it lengthwise into roughly reed-tongue-sized blanks, you can clamp one end of each blank in a vice and use pliers to grip the other end while manipulating it to take out any twist and bend it straight.

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Beware it is likely to instantly and violently unroll itself if you simply cut the band that holds it together (and to make matters worse it may have razor sharp burrs on the edges). 

Do not, under any circumstances, cut the external retaining band fitted to coils of spring steel.

Always cut pieces from the inner end of the coil using good substantial snips. 

 

Geoff 

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  • 1 month later...

Tom, my maximum is .0015 inches/side, but minimum is .001”.  I can do tighter, but the high harmonics go up too much and the centering accuracy needed for pitch stability becomes substantially harder since an error of .0001” is a much larger percentage of a very small gap.  Very small gaps increase the chance of a reed buzzing or impinging on the frame.  This will affect single reed shoes with narrow window sides more than a plate with wider metal at the perimeter, and affects longer reeds more compared to short ones.
   Smaller clearances can increase responsiveness, but I find there is a limit to their utility.  Tight clearances also require progressively more careful and difficult fitting with decreasing benefit.

   On the other side, wide gaps rapidly decreases reed responsiveness and makes for poor reeds.  The ideal is to find the clearance that produces your best playability and tone results and to try to reproduce that to very small tolerance, say +/- .0001” or .0025mm ( then center it as perfectly as you can )

   I recently made 16 new tongues to match badly rusted Wheatstone reeds in the 5th and 6th octave range, and did those to .0007”/side but these were small to tiny reeds, so the small gap was more proportional to their length.  

Dana

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  • 5 months later...

I see that some laser cutting companies will provide spring steel,  like this one provides 1095 spring steel, hardened or annealed, 0.01" for instance. I put in a rough plan of a bandoneon reed and it came back with a $20 setup fee for each reed size and then about $1 a reed. There are about 17 sizes of reed on an bandoneon (and of course 284 reeds!). I might want to try a few of these as an experiment for replacing bad reeds. I'm not an engineer though - what am I missing :)  I think the cutting method was described as fiber laser. So would that ruin the temper of the steel? 

 

https://app.oshcut.com/catalog/steel/1095-spring-steel-hardened

 

They also have various options for printing reed plates and that was a bit more complicated but I think zinc worked out at $100 a plate including setup.

Edited by paulbrennan
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