[pianotech] snugging up an agraffe

[Ron Nossaman]

On 10/4/2010 6:44 AM, Ed Foote wrote:
>   Greetings,
> I wrote:
> " The threads would strip before I could snug them sufficiently in
> position."
>
> Andrew asks:
>  >>seems to me that you would file the bottom of the agraffe or
> countersink a little to have an agraffe snug up at the desired angle to
> the strings. Am I missing something here? pushing brass to the point of
> stripping the threads seems to miss a step... <<
>
> How much is too much when seating the agraffe? I bend metal in the last
> few degrees. I think I can feel the metal in the tapered bottom skirt
> give a little bit when I apply the final squish. Since it is tapered,
> there is an initial give that rapidly grows stiffer. With some practice,
> I can usually get them to seat right at the right angle at the precise
> moment they get "hard'.

That's not a bad description. I find about 45° past snug to be a decent 
target. If the spot face counter bore seat isn't perpendicular to the 
stem hole, it'll take a bit more


> Even when one alters the agraffe to fit, you still have to apply a
> certain amount of torque to seat it. I sense torque with my hands when
> installing agraffes,and when the feel goes soft,(threads beginnng to
> bend away from the skirt), well before what I know to be a trustworthy
> and solid seating has occurred, I measure.

I find it unnecessary to alter agraffes for alignment. Make yourself a 
tool to spin them in and out quickly, and have a half dozen more 
agraffes of any given needed configuration than you need on hand, and 
you have what you need without alteration. Just gotta get the right 
agraffe in the right hole.

You measure what, and how?


>And yes, the undersize
> contributes to this problem, a lot.

I don't see how. I've yet to strip an agraffe thread, nor see how it's 
possible with the fit mismatches reported. How does the thread fit 
interfere with alignment?


> I like to put a small touch of grease or wax on the threads, so that the
> top of the stem isn't being stressed by friction as I flatten the skirt
> to order.

I use a drop of oil, but that's for the threads running into the iron, 
so they spin in and out more easily. I can't see how that alleviates 
stress at the top of the stem as the skirt contacts the counter bore.


> When the agraffe comes to its final position, it needs to be as tight as
> possible without damaging the stem.

According to? I know people who crank them down much more than I, and 
others that make them just barely snug. None of the above have a record 
of either failure, or noise by the detriment of having not having been 
tightened enough. This seems like a good time to ask a question I've 
been carrying around for a very long time waiting for an opportune time 
for insertion. Has anyone reading here ever actually found an agraffe 
that made noise that was verifiably found to result from not having been 
tightened enough? I've found agraffes that were finger movable without 
string tension, that didn't make objectionable noises, and have NEVER 
found an agraffe noise attributable to having not been tightened down 
enough.

So what's the real story? Any rationally evidential contributions out 
there.
Ron N