[pianotech] problem in mating hammers to strings

[Paul McCloud]

Hi, Ron:
	If you file the hammers square to the sides, and they are hung so that
they are level to the keybed at the letoff point, your problem is the
agraffes/strings/whatever.  Alternatively, if your strings are level (use a
level) and they don't mate the hammers, then your hammers aren't hung
properly.  They should have a slight cant on the rest rail (ok, just off
the rest rail).  If you don't use a level, you can hold a 6" rule loosely
in your fingers so that it hangs vertically and lower it onto the strings
like a plumb bob.  You'll be able to tell if the strings are in the same
plane and level if you pluck them.  Feeling the strings is not that
accurate.  You should use something to verify whether they are in the same
plane.  I think there's a tool which sits on the strings which holds a 6"
rule so it can sit on the strings.  It's not a level, but will hold it
perpendicular to the strings so you can check by plucking.  
	One question.  Has anyone before you leveled the strings?  The reason I
ask is that there is a device called a Strait Mate that is used to push up
on the strings from below in the action cavity.  You know this tool?  In
the past, some of these were manufactured improperly, and they actually
caused the strings to become unlevel, though they were basically in the
same plane.  The problem was that the nylon roller was not level to the
base of the device.  If you're not familiar with the Strait Mate, I think
Pianotek sells them.
	Grasping for straws...
	Paul McCloud
	San Diego


> [Original Message]
> From: David Nereson <da88ve at gmail.com>
> To: <pianotech at ptg.org>
> Date: 03/03/2011 4:48:14 AM
> Subject: Re: [pianotech] problem in mating hammers to strings
>
>     I feel to see if all the strings are in the same plane.  I 
> don't like the idea of the bubble level because if the floor 
> isn't perfectly level and the plate isn't perfectly level, or if 
> the holes in the agraffe aren't perfectly level, you're getting 
> a false indication.
>     But regardless, when viewing the hammer line at the strike 
> point, it should appear as a straight line, so that's how I 
> filed them.  I then held hammers against the strings, plucking 
> the strings, and still found indications that the hammers had 
> high areas, or that a right string was low, and again, almost 
> all in the low tenor, and all on the right side of the hammer. 
> So I used the plexiglass paddle with a thin (3/16") strip of 
> sandpaper glued to it, as demonstrated by either Andre Oorebeek 
> or Ben Gac, I believe, to file down the hammer in the area that 
> damps the strings that don't ring when plucked.
>     This results in hammers that have a "step" in the strike 
> point surface, but using the end of a steel rule and a bright 
> light, I did not observe any low ("unlevel") strings in the 
> corresponding unisons.  I still wonder if the pressure of 
> holding an angle-bored hammer against the unison causes the 
> shank to flex or the hammer to lean.
>     --David Nereson, RPT
>
>