Tuning Hammer Technique and Staibilty Question

[Robert Finley]

I would like to ask a question about how the tuning hammer should be used to achieve a stable and accurate tuning. I understand that one has to turn the tuning pin with the hammer so that the string is slightly above pitch, and then ease it back down into position, presumably to eliminate any self-twisting of the pin that could occur afterwards, causing the string to go out of tune. I guess this is because the tuning pin is flexible and the twisting at the bottom of the pin where it is seated in the pin block lags the twisting at the top of the pin over which the tuning hammer is placed. 

My question is, how much should one tune the string above pitch before easing the pin back down? Should it be a few cents, cycles or what? I find it interesting that the tuning pin is that flexible because it seems to be made of rigid steel. I would expect the twisting effect of something that rigid to be minute, but enough to cause a string to go out of tune if the incorrect hammer technique is used. I have found that on my own piano, I can turn the tuning hammer a noticeable amount without a change in pitch, until I reach a point where it does start to change. 

Thank you for your advice. 

Robert Finley
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