Key Leads and Inertia

[David Love]

John:

If you find excessive flex in the key, how do you address it.

David Love
davidlovepianos@earthlink.net


> [Original Message]
[link redacted at request of site owner - Jul 25, 2015]
> To: Pianotech <pianotech@ptg.org>
> Date: 5/1/2003 2:26:34 PM
> Subject: Re: Key Leads and Inertia
>
> Ron Nossaman wrote:
>
> > Del,
> > You knew this was coming, so I won't make you wait any longer. Do you 
> > have any rough rule of thumb go - no go diagnostic criteria for
deciding 
> > when keys are too flexible during teardown?
> > 
> > Ron N
>
>
> Ron, I hope you don't mind if I weigh in on this. I use a 1000g weight 
> applied to the end of the key (naturals). If the weight bends the key - 
> measured with a dial indicator - more than 1mm I consider it to be a 
> problem, ideally is should be under 0.75mm. The key is removed from the 
> key frame and placed on a work bench. The key is supported under the 
> balance rail hole and under the capstan. A clamp is place to hold the 
> key down near the capstan. The weight dangles from a cord off the 
> playing end with an indicator close by it. The weight is slowly lowered 
> and a reading is taken. Average several reading to find the key flex.
>
> I derived the 1mm using data in Pfeiffer's book "The Piano Hammer". 
> Using the force applied to the key during load play I came up with a 
> figure that would bend the key 10mm. This along with personal experience 
> led to my rule - no more flex than 1mm at 1000g.
>
> John Hartman RPT
>
> John Hartman Pianos
[link redacted at request of site owner - Jul 25, 2015]
> Rebuilding Steinway and Mason & Hamlin
> Grand Pianos Since 1979
>
> Piano Technicians Journal
> Journal Illustrator/Contributing Editor
[link redacted at request of site owner - Jul 25, 2015]
>
>
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