[pianotech] agraffe replacement

[Alan Eder]

I last got agraffes of the crushable perimeter type--and a counterbore for reduction of height upon contact with the plate--from Pianotek.


A taut string coming through the appropriate bridge pins and corresponding hole in the agraffe being installed make it easy to get the 90 degree angle by sight--no special jig needed.  For uniform agraffe height, I use straight pieces of solid metal that span three, five and seven agraffes.  If you can install the agraffes so that these mini-straight edges neither rock (on a higher agraffe) nor reveal a gap between top of agraffe and bottom of straight edge, you get a cookie (or whatever your personal culinary equivalent is of a job well-done!).  One caveat: there remains the possibility that the holes in the agraffes are not an absolutely uniform distance below the part (the top) that I am measuring.  Have not yet found a worthwhile way to reign in that potential variable.


Alan Eder


P. S. I highly recommend getting a few extra agraffes and conducting a couple minutes worth of valuable research that will guide you in your work.  Tighten one down to when it contacts the plate, then keep going, paying careful attention to the sound it makes and how it feels.  Continue until it breaks, and calibrate your operation accordingly.


-----Original Message-----
From: John Delacour <JD at Pianomaker.co.uk>
To: pianotech <pianotech at ptg.org>
Sent: Sun, Jul 17, 2011 8:29 pm
Subject: Re: [pianotech] agraffe replacement


At 20:12 +0000 17/07/2011, you wrote:

>we have to replace an agraffe set in a 1960's Hamburg Steinway D.
>I was curious about which is your method to do so. This is my first 
>time to install a Steinway ones:
>
>I was tought they should be:
>- 90 degrees squared to the string
>- With uniform height.
>
>About the 90 degrees: do you use a jig? how do you build this kind 
>of jig? Just install by sight without jigs at all?

You can use lengths of wood about 12 x 3 in cross-section with the 
end perfectly square running from the bridge pins to the agraffe, but 
doing it by eye is not difficult.

>About the uniform height: do you take off only the odd numered 
>agraffes first and install the new ones with the original even 
>numbered agraffes as reference? Or is that not neccessary at all?

It is not guaranteed, especially on a 1960s D, that the agraffes were 
originally at the right height.

>We are using original Hamburg Steinway agraffes 5.5 mm. How big is 
>the turn we are able to do after the agraffes is contacting the iron 
>frame without risk / break the agraffe? Do you prefer to reduce the 
>iron frame to lower the agraffe or to install shims under the 
>agraffe to raise it up?

Some new agraffes have a flat bottom but some have the bottom angled
|/ \| so that only the perimeter is in contact with the iron plate. 
These have the advantage that when you tighten them right down, the 
brass at the perimeter will crush, allowing you to get the agraffe 
square without applying dangerous torque.  You can also put the shank 
in a drill and pare down the outer pressure ring with a hard tool to 
allow the agraffe to go lower without excessive torque.

I've looked at Jahn's and Baumgärtel's catalogues and neither of 
them mention the two types, and I can't remember who supplied the 
last set I installed.

JD


 
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