[pianotech] Agraffe Washers

[Overs Pianos]

Hi all,

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

For those who have a lathe, it is easy to turn up custom washers with 
a sharp parting tool. A narrow parting tool can be used to part off 
washers to exactly the thickness required. Wal and I do the agraffe 
fitting in our shop. Wal fits them to the plate while I work the 
lathe producing the washer thicknesses that he calls for after the 
first 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 OD and ID 
required (use either free machining brass or SAE 1214L as working 
stock)

2) Sharpen a narrow width parting tool (I use a 2.5 mm wide cutter - 
don't use throw away cutters - they are not sharp enough)

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

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

5) Measure the thickness of the resulting washer with a micrometer. 
You can now calculate the effective parting-off loss due to the 
cutter width. It will be, the amount the cutter was advanced towards 
the chuck minus the thickness of the test washer.

The reason for going through this five step procedure before making 
the custom washers is to determine exactly how much stock is lost for 
each advance of the cutter from one washer to the next. Lets say that 
the cutter loss is determined to be 95 thou (our 98 thou [2.5 mm] 
cutter will become narrower as we sharpen away more of the tool). 
Knowing this we can produce a 2 thou washer 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 where the last part-off was 
made. Using this procedure, we can use up the entire 80 mm of sleeve, 
losing only the cutter width between each successive washer.


You can now part off washers down to a couple of thou in thickness up 
to whatever you require. Don't worry about the thinner washers 
curling up a bit when they are parted off. They'll soon flatten out 
when they are compressed between the agraffe and the iron plate 
counterbore.

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

Hope this helps.
Ron O.


>On 3/12/2012 10:38 AM, Nicholas Gravagne wrote:
>>List,
>>
>>Am I not remembering right, or was there a time past when 0.007" thick
>>agraffe washers were available? Pianotek carries 0.020" and 0.012",
>>while Schaff carries 0.010".
>
>
>Steinway sells 0.021" and 0.030", according to the 2011 parts list, 
>but I don't remember any 0.007" from anyone. Maybe John Ford or some 
>such, now long gone. But I almost never use them, so I'm not much of 
>an information source there.
>
>Ron N


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