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Piano keyframe consists of these parts:

enter image description here

The balance rail is marked (6) in the image, but there are two balance rail pin rows - in the picture only the pin row for white keys is marked(7).

You can clearly see two rows of balance pin rows (with red felt around them) - one for white keys and one for black keys:

Piano action

What's the distance between those two rows? What's the offset?

I’m asking because I want to make a piano action.

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    I'd expect that it isn't standardised and that different manufacturers and different models will have different distances
    – DavidW
    Aug 21, 2022 at 9:51
  • This seems like the type of question where some more detail on why you're asking would be helpful.
    – Aaron
    Aug 21, 2022 at 14:03
  • @Aaron How does it help you in answering the question? You either know the distance between those pins (on any specific piano(s)) or you don't. But in this particular case it' s because I want to make piano action from wood.
    – JBeurer
    Aug 21, 2022 at 15:10
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    That's immensely helpful, because what you really need is not the distance, but how to calculate the distance based on the other dimensions of your action. You might actually be better off finding a junk piano, pulling it apart, and copying its action.
    – Aaron
    Aug 21, 2022 at 17:49
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    The reason for wanting more detail is this isn't a piano building forum. Aug 23, 2022 at 13:02

1 Answer 1

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The balance rail and fulcrum point of the keys must produce an even feeling between black and white keys. White keys are longer and heavier than black keys so that is why their fulcrum point is further from the action and closer to the keyboard.

I’m not a piano designer or tech but the distance between the balance points must be different for different brands and models and is determined when the piano is designed based on the length, weight and balance point of the keys. From your diagram it looks as if the balance point is close to the center of the key. That means that a longer key will give you a larger distance between the balance points of the white and black keys.

The offset is probably roughly determined by the overall length and weight of the black and white keys. I can’t say exactly what that would be but logically it should be about half of the difference of the key’s overall lengths. Allowances would also have to be made for the difference in weight, especially since white keys have more mass on the playing end.

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    "probably different for different brands and models and is determined when the piano is designed based on the length, weight and balance point of the keys": indeed, the key dimensions are not the same in different pianos.
    – phoog
    Aug 21, 2022 at 17:20
  • @phoog I re-worded that section a bit, thanks for your comment! Aug 21, 2022 at 17:35
  • Meanwhile, I found What are the dimensions of piano keys, in inches?
    – phoog
    Aug 21, 2022 at 17:40
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    The pins are offset from the actual balance points, and their placement depends on additional factors like the bushings around them.
    – Aaron
    Aug 21, 2022 at 17:51
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    Looks like the amount and placement of the leads is also important for key balance. And I would guess each key might be individually balanced (using the leads) based on the hammer and desired feel for the particular note. Aug 23, 2022 at 13:32

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