Reed tongue replacement

[DjB]

 

I was recently passed a Lachenal EC and while I opened the box to unclog some of the reeds which were not producing sound, I noticed that that 2 notes actually have broken reed tongues. Could someone please advise where I may be able to find replacement ones in the UK or how to make one? The bit im unsure of with making is thickness to start with. Is  0.7mm or 0.8mm a good starting point for brass? I was considering using the natural frequency formula for vibrating cantilever but air resistance and inertial loading would change it anyway so can it be used as starting point and tuned by just sliding the tongue? Are there any other proven methods? 
 

thank you

Edited March 21 by DjB
Wrong technical terminology used

[d.elliott]

usually sourced from scrappers, I assume the reeds are brass. You make your own new reeds from brass stock cold forging the brass to work harden it first. 

[DjB]

Hi @d.elliott it is actually the reed tongue. Are there any instructions around on how to make a new reed tongue? By hardening I guess you mean cold hardening like hard burnishing. The bit im unsure of what thickness to start with. Is  0.7mm or 0.8mm a good starting point? I was considering using the natural frequency formula for vibrating cantilever but air resistance and inertial loading would change it anyway. Thank you

Edited March 21 by DjB

[alex_holden]

38 minutes ago, DjB said:

Hi @d.elliott it is actually the reed tongue. Are there any instructions around on how to make a new reed tongue? By hardening I guess you mean cold hardening like hard burnishing. The bit im unsure of what thickness to start with. Is  0.7mm or 0.8mm a good starting point? I was considering using the natural frequency formula for vibrating cantilever but air resistance and inertial loading would change it anyway. Thank you

 

You're better off trying to match the profile of the other reed in the same instrument with the same pitch, or if they are both broken, copy the next pitch up and make the tip slightly thicker. Measure the thickness at several places along its length using a point micrometer. The difficult part is filing the edges to get a very close fit in the vent slot without it being so close that it rubs. If it's an old reed frame with rusty screws you might need to use heat to loosen them otherwise they can shear off when you try to unscrew them.

[DjB]

thanks @alex_holden, that is very helpful.

[d.elliott]

10 hours ago, DjB said:

Hi @d.elliott it is actually the reed tongue. Are there any instructions around on how to make a new reed tongue? By hardening I guess you mean cold hardening like hard burnishing. The bit im unsure of what thickness to start with. Is  0.7mm or 0.8mm a good starting point? I was considering using the natural frequency formula for vibrating cantilever but air resistance and inertial loading would change it anyway. Thank you

Not any form of burnishing, by cold hammering to break up the metallographic structure