bore distance: was Re: hammer replacement

[Newton Hunt]

Hi David,

The shank should be slightly below horizontal when the hammer is resting on
the string.  By measuring string height and center pin height, subtract the
shorter from the longer and you have the bore distance when the hammer is
against the string, optimum, then at about 1/32 inch for future filing. 
When filing initially the hammer will expand to maintain original
dimensions.

		Newton

David Love wrote:
> 
> Newton:
> 
> Another issue is the starting point for the shank.  Boring to the let-off
> point positions the shank slightly higher and reduces resistance at the
> beginning of the key stroke effectively reducing the force required to get
> the key moving.  (I'm sure there's a more technical explanation)
> 
> David Love
> 
> >From: Newton Hunt <nhunt@optonline.net>
> >Reply-To: pianotech@ptg.org
> >To: pianotech@ptg.org
> >Subject: Re: bore distance: was Re: hammer replacement
> >Date: Fri, 29 Jun 2001 09:41:16 -0400
> >
> >Hi David,
> >
> >Interesting question you raise.
> >
> >I always calculate to string height because that is where the engineer
> >determined the optimum mechanical advantage for the action.
> >
> >But...
> >
> >If you measure from bore center to strike point then add 1/8" to an
> >imaginary line, that line represents the optimum regulation height for
> that
> >hammer.  No matter whether that point is below or above the actual string
> >height.  So, taking that in reverse...
> >
> >               Newton
> 
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