Re: [Harp-L] On Tolerances

[Pierre <plavio@xxxxxxxxxxxx>]

Perhaps I can act as a tie breaker, everything I read about embossing seemed 
to imply that it is done on the sides at least that is what I understood or 
assumed.

Doing the tip seems futile as the tip is narrow and therefore not much of a 
factor, also the burr on the tip would not help much once the reed has swung 
past the burr.

I gap my stock harmonicas quite close and I tried embossing once with a 
penny and noticed no difference. So either I did it wrong or embossing does 
not do nearly as much as proper gapping and arcing of the reed.

BTW seems to me that copper is really soft and not a good tool for 
embossing, also the edges of pennies are rounded. My son speed skates and 
speed skates are sharpened by hand on a jig. Sharpening the skates creates a 
burr on the edge of the blade. When there is burr all along the blade, the 
skate is sharp. Of course, before skating, the burr must be removed. Various 
tools are used to do this including rasor blades or a flat sharpening stone, 
etc. Anyways the best tool to remove the burr seems to be a carbide tool 
with a 90 degree edge. I guess because it is so hard. So perhaps the best 
tool for embossing would be a carbide cylinder. Of course carbide is very 
expensive, so perhaps a stainess steel cylinder would be best.

Pierre.





----- Original Message ----- 
From: "Ludo Beckers" <ludobeckers@xxxxxxxxxxx>
To: <harp-l@xxxxxxxxxx>
Sent: Friday, February 04, 2005 9:58 AM
Subject: Re: [Harp-L] On Tolerances


> Siegried wrote:
> << I stick to what I said about embossing just this part of the slot and 
> not its sides. <<
>
> Hi again Siegfried, I still disagree. This is how "embossing" is explained 
> in brief on www.thenhole.com :
>
> A very effective modification is the narrowing of the slot (embossing). 
> The reed slot is narrowed by pressing a round metal object along the sides 
> of the slot, causing them to bend inward slightly.
>
> A popular tool to use for this is the back of a tuning fork. The round 
> ball at the end of the fork is placed on top of the reed and is moved 
> along the reed while gently pressing down. This is delicate work and a few 
> passes are usually required.
> Hold the plates up against the light to check the clearance between reed 
> and slot.
>
> If the reed gets stuck, check for rough edges either on the reed or the 
> slot edges.
> If the slot becomes to narrow it can easily be pushed back with the tip of 
> a small screwdriver.
>
> Narrowing the slot increases the overall responsiveness of the reed and 
> reduces leakage when the reed is choked. The reduced leakage has a very 
> big impact on overblow playing.
>
>
>
> <<I think it´s necessary to clarify the understanding of the term "gap" 
> before explaining my view point. We certainly agree that "gap" is the 
> distance between reedtip and slot wall? <<
>
> No, I don't agree. Gapping is altering the offset; the distance between 
> reed and reedplate.
>
> << A fixed reed has 4 kinds of tolerances which are partly necessary 
> partly can cause anger. The most important is of course the offset = the 
> distance of the reedtip to the plate surface and is even crucial for 
> starting the vibration.<<
>
> Not sure what you mean by "anger" here. In your language I believe it 
> means "böse".
>
> <<Important is also the tolerance of the reed sides or edges to the 
> longitudinal slot walls. <<
>
> Exactly!
>
> << Note: It isn´t advisable to emboss the slot sides because the tolerance 
> here is a fraction of a mm and one risks that the reed sticks.<<
>
> If the embossing is done overzealously, the sticking reed can easily be 
> freed with a feeler gauge.
>
> <<Well, Ludo, the term "embossing" doesn´t point to the spot where the 
> embossing is performed, it´s just a kind of working a metal surface, no 
> more no less.<<
>
> I agree, but applied in harmonica jargon I believe we still misunderstand 
> one another here :-)
>
> Ludo
>
>
>
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