Drilling for key leads and key flex

[Dean May]

Think I-beam. Nearly all of the stress is carried by the outer fibers.
Drilling through the middle will have negligible effect on the
structural integrity. All of the bending load is carried by the top
layer and bottom layer.

Further, the maximum stress occurs in the middle of the key right at the
key pin hole. The biggest cause of key flexure is the slot cut into the
key right at the point of max stress. Where you need it the most there
is the least section across the top. This is why putting on good key
buttons securely yields big improvements.


Dean
Dean May, BSME, PE             cell 812.239.3359
Engineer in my former life (they just never let me blow the whistle)
PianoRebuilders.com   812.235.5272
Terre Haute IN  47802


-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Farrell
Sent: Thursday, December 01, 2005 8:15 AM
To: Pianotech
Subject: Re: Drilling for key leads and key flex

I don't know for sure, as I am not an engineer, but it sure seem likely
to 
me that a hole drilled half-way through the key will induce half the
flex 
that a hole drilled completely through would induce. However, if flex is
the 
concern, I should think that if you glued/epoxied the lead in place,
then no 
flex would be induced - or rather the change in flex would be limited to
the 
flex difference between spruce and lead (good golly, what would that
be?).

So there's my half-cent worth (or worthless, as the case may well be).

Terry Farrell

----- Original Message ----- 
> When installing keyleads in new keys, will there be any significant
> difference in key flex if you drill the holes all the way through
versus
> not.  Let's assume for arguments sake that the holes are located in
the
> center of the key.
>
> David Love


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