[CAUT] BAck ckeck pullers (was:balancier/wippens report)

[Jeff Tanner]

On Dec 19, 2006, at 10:35 AM, Jon Page wrote:

> >any chance of supplying one of the snap ring pliers
>
> I use the plier type upright hammer head extractor to lift them.
> --  
>
> Regards,
>
> Jon Page
>


Have any of you had any issues with S&S backchecks, once pulled,  
being driven back down by checking?  I'm thinking that once  
extracted, the grip the backcheck has on the wire would be weakened  
and the backcheck height would become unstable.

I've done it on one piano that was a real problem, but have no way to  
measure whether the backchecks have been driven back down.  I was not  
comfortable pulling the backchecks.  IMO, backcheck height should be  
a constant.  Once hammers are replaced, the backcheck height would  
have to be readjusted.

By the way, I used small vice grips clamped to the bottom of the wire  
and a screw type vertical hammershank puller.  Rebending and  
regulation is required.  But if you don't use the vice grips it  
really distorts the backcheck wire bends.

Tim Coates wrote:
>  The shank at rest should dissect the backcheck at the line that  
> separates the top third from the middle third.

Wouldn't this "rule" completely depend on the relationship of the  
tail length to the overall length of the hammer and where the boring  
on the hammer is in relationship to hammerblow distance?

If all the regulation specs (including checking) are "correct" with  
new hammers, then as hammers are filed, compensations must be made so  
that hammer shank height remains constant, or proper checking will be  
an increasing problem with each filing of the hammer.

Jeff


Jeff Tanner, RPT
University of South Carolina



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