[Harp-L] Curvature of the mouthpiece

Vern jevern@xxxxx
Mon Jul 4 05:06:44 EDT 2016

You should bend the arch after milling & polishing but before plating.

Clamp it against a curved form  You can make the form of wood... mark with a compass and cut on a bandsaw.

Measuring the radius of the curve of the existing mouthpieces is an interesting trig problem.  I won’t burden you with the derivation but my solution follows.  You can check it by placing the measured mp against the marked curve. 

Let R = the radius of the mouthpiece curve
Let D be the depth of the curve at the midpoint of the mp.
Let L be the length of the mouthpiece, (the chord measured with a straight ruler.)

Then R = L * L / 8 / D  +  D / 2

Example: L = 5.5”
                D = .12”
                R = 5.5 * 5.5 / 8 / .125 + .125 / 2  =  31.3”

The radius of the form must be slightly less than the radius of the desired mp curvature to allow for spring-back of the metal. Start with 90% of the calculated radius and cut-and-try with shorter form radii until you get the desired mp curve.

> On Jul 3, 2016, at 9:15 PM, Li Leon <leon.issac.li at xxxxx> wrote:
> Hi experts,
> One of my friend is kindly offered to make me some mouthpieces, to replace
> me worn and not so comfortable old ones.
> Just wondering whether anyone knows by any chance how the curvatures on the
> these mouthpieces are formed and whether it is pre or post milling/molding.
> Also, what thickness would be the standard/recommended for the coating, I'm
> getting quote for silver plating but the price seem to vary quick a bit as
> the thickness increase.
> Any information on the above points is greatly appreciated!
> Thanks in advance!
> Cheers,
> Leon

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