[pianotech] Agraffe Washers

[Ed Foote]

Greetings, 
    Or..... you can take a normal shim, place it in a recessed hole that is the correct thickness you want,(bored in something harder than brass and softer than a file,  and pass a file over the top.  it takes all of 10 seconds to reduce a .021 shim to whatever you need.    If it is needed so thin that the file will tear it up, a flat sanding disc of 320 grit wet or dry sandpaper in the drill press will do the same thing. 
   However, I do prefer the hollow endmill method of trimming the agraffe. 
Regards,


Ed Foote RPT
http://www.piano-tuners.org/edfoote/index.html



-----Original Message-----
From: Overs Pianos <sec at overspianos.com.au>
To: pianotech <pianotech at ptg.org>
Sent: Mon, Mar 12, 2012 3:20 pm
Subject: Re: [pianotech] Agraffe Washers


Hi all,


Agraffe alignment is always a pain without some facility to makecustom thickness washers. I don't find OEM washers to be very usefulmost of the time, because the thickness required invariably isn't thethickness of the washers available.


For those who have a lathe, it is easy to turn up custom washerswith a sharp parting tool. A narrow parting tool can be used to partoff washers to exactly the thickness required. Wal and I do theagraffe fitting in our shop. Wal fits them to the plate while I workthe lathe producing the washer thicknesses that he calls for after thefirst nip-up of each agraffe which requires shim adjustment.


The procedure for turning is;


1) Turn up a sleeve of approx. 80 mm in length to the ODand ID required (use either free machining brass or SAE 1214L asworking stock)


2) Sharpen a narrow width parting tool (I use a 2.5 mmwide cutter - don't use throw away cutters - they are not sharpenough)


3) Make a parting cut of minimum width, such that the toolis cutting with both outside edges of the tool in thestock.


4) Advance the cutter down the bed towards the chuck,using the compound slide, by the width of the parting tool plus 20thou, noting the total number of thou the compound slide wasadvanced.


5) Measure the thickness of the resulting washer with amicrometer. You can now calculate the effective parting-off loss dueto the cutter width. It will be, the amount the cutter was advancedtowards the chuck minus the thickness of the test washer.


The reason for going through thisfive step procedure before making the custom washers is to determineexactly how much stock is lost for each advance of the cutter from onewasher to the next. Lets say that the cutter loss is determined to be95 thou (our 98 thou [2.5 mm] cutter will become narrower as wesharpen away more of the tool). Knowing this we can produce a 2 thouwasher by advancing the cutter 97 thou down the bed, then parting off.For a 5 thou washer we advance the cutter another 100 thou from wherethe last part-off was made. Using this procedure, we can use up theentire 80 mm of sleeve, losing only the cutter width between eachsuccessive washer.




You can now part off washers down to a couple of thou inthickness up to whatever you require. Don't worry about the thinnerwashers curling up a bit when they are parted off. They'll soonflatten out when they are compressed between the agraffe and the ironplate counterbore.


This might sound like something of an effort, but if you fit mostof the agraffes using a power screwdriver to determine those agraffeswhich can be fitted without the need of a washer, you'll usually onlyhave about 6 to 10 agraffes which require a thin washer the get theremaining agraffes to the correct position for pre-loading toalignment.


Hope this helps.
Ron O.




On 3/12/2012 10:38 AM, Nicholas Gravagnewrote:
List,

Am I not remembering right, or was there a time past when 0.007"thick
agraffe washers were available? Pianotek carries 0.020" and0.012",
while Schaff carries 0.010".



Steinway sells 0.021" and 0.030", according to the 2011parts list, but I don't remember any 0.007" from anyone. MaybeJohn Ford or some such, now long gone. But I almost never use them, soI'm not much of an information source there.

Ron N




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