Keyframe Bedding

[David Skolnik]

Requesting a little perspective:
What are the deficiencies of the Steinway method of setting glide bolts?

Establishing the practical parameters of frame 
bedding, once I've established defined contact to 
effectively preclude any knocking, how much 
additional stress could I introduce into the 
system before beginning to observe negative effects?  :
         - increased resistance of una corda shift
         - premature squeaking at glide contact
         - increase in friction and wear of 
keyblock plates and frame guide pins
         - change in keydip, aftertouch,
         - create knocking at front rail or back rail

Regarding dags:
         - are dags essential to proper function 
of the action? i.e.: would back rail [necessarily] slap in their absence?
         - how much force (at glide bolt) would 
be required to compromise otherwise firm contact 
of back rail, to the point where        firm capture by dag is required?
         - if the dags are used to compensate for 
insufficient care in back rail bedding, then wear 
and seasonal variation could         allow for 
the slap of Jude's observation.  (another cause 
could be flat, un-arched front to back profile).

I'm not sure that Andre's tuning fork analogy is 
operational here.  I would need to hear a more thorough explanation.

I do love finding new uses for my 
caliper.  Especially fond of them in key leveling.

David Skolnik
Hastings on Hudson, NY


At 10:29 PM 7/7/2008, you wrote:
>I've experienced the tonal improvement but I've 
>also noticed an occasional increase in the 
>volume of keyslap on the backrails and sometimes 
>extra knocking in the treble hammers. To my 
>knowledge, the backrail was well secured by the 
>dags and it's definitely not keyframe knocking.
>
>Jude Reveley, RPT
>Absolute Piano Restoration, LLC
>Lowell, Massachusetts
>(978) 323-4545
>
>
>----- Original Message -----
>From: "andre oorebeek" <<mailto:oorebeek at planet.nl>oorebeek at planet.nl>
>To: "Pianotech List" <<mailto:pianotech at ptg.org>pianotech at ptg.org>
>Sent: Monday, July 07, 2008 5:41 PM
>Subject: Re: Keyframe Bedding
>
> > And, turning the bolts tighter also increases the tension in the tone.
> > The bolts are in a way like tuning forks.
> > If you press down a tuning fork hard on a wooden surface, the tone it
> > generates will intensify.
> > That way it is possible to 'voice' by adjusting the bolts.
> >
> > friendly greetings
> > from
> > André Oorebeek
> >
> >>
> >> -----Original Message-----
> >> From: <mailto:erwinspiano at aol.com>erwinspiano at aol.com
> >> To: <mailto:ilvey at sbcglobal.net>ilvey at sbcglobal.net
> >> Sent: Mon, 7 Jul 2008 2:33 pm
> >> Subject: Re: Keyframe Bedding
> >>
> >> The key frames in modern grands all have a somewhat arched/pinched
> >> key frame arrangement  front to back & end to end. Adjusting the
> >> bedding bolts to a neutral position to start with & then turning the
> >> bolts tighter against the key bed is where the stressing comes
> >> from.  You can measure the subsequent rise at the front of the keys
> >> as the bolts are being turned as  per Jon Pages suggestion.  The
> >> back of the frame is held down by the dags & the ends by the key
> >> blocks
> >>   Actually this is also a bit of a buffer or safety factor for
> >> climate changes. This way the bolts will hopefully stay in contact
> >> with the bed in each season & not be so prone to change with
> >> humidity & temp.
> >>   Dale
> >>

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