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Step 14Weighting the keys
The keys often don't fall the right way by themselves, either for mechanical reasons or for how the action is supposed to feel when it's played. Usually this is adjusted by adding lead weights to increase the weight on one side of the balance rail, but more flexible systems have been designed using springs, and more recently magnets.
In grand pianos skilled factory workers carefully position key weights by hand with the action all assembled so it takes a specified minimum weight to make each key move. This would have been impossible to do with my keys anyways, but recently this subject has been explored a little further, which you can read about here and here. My keys were all front heavy but in this kind of action they need to be back heavy by as much as 15 grams and return to rest by themselves so that they repeat and have the right amount of resistance, and one of the only places to put weights would have been inaccessible since it's directly below one of the action rails.
Ordinarily pre-made conical weights are pressed into holes drilled in the sides of the keys, but I didn't have any ones small enough. Davies suggested pouring molten lead into the holes and swedging them, but instead I made some old ones narrower by pressing them flat with an arbor press. I used a plate of harder metal to stop the ram at the right thickness.
I checked the resulting weights at the front with a couple uniformly spaced sample weights for four different pairs of neighboring natural and sharp keys and just drew lines connecting the positions I had marked out. I made a little jig to drill the outside holes for the leads, with a cut off nail to hold the jig in place, and opened the wood between them with a sabre saw chucked in the jigsaw and squared the sides with a chisel. I pressed the weights in with a drill press and snipped the excess off with some flush cutting shears. I used a third weight placed much closer to the balance rail to bring the keys to the final weight, but positioned them individually to make up for the differences from the widths of the keys.
In grand pianos skilled factory workers carefully position key weights by hand with the action all assembled so it takes a specified minimum weight to make each key move. This would have been impossible to do with my keys anyways, but recently this subject has been explored a little further, which you can read about here and here. My keys were all front heavy but in this kind of action they need to be back heavy by as much as 15 grams and return to rest by themselves so that they repeat and have the right amount of resistance, and one of the only places to put weights would have been inaccessible since it's directly below one of the action rails.
Ordinarily pre-made conical weights are pressed into holes drilled in the sides of the keys, but I didn't have any ones small enough. Davies suggested pouring molten lead into the holes and swedging them, but instead I made some old ones narrower by pressing them flat with an arbor press. I used a plate of harder metal to stop the ram at the right thickness.
I checked the resulting weights at the front with a couple uniformly spaced sample weights for four different pairs of neighboring natural and sharp keys and just drew lines connecting the positions I had marked out. I made a little jig to drill the outside holes for the leads, with a cut off nail to hold the jig in place, and opened the wood between them with a sabre saw chucked in the jigsaw and squared the sides with a chisel. I pressed the weights in with a drill press and snipped the excess off with some flush cutting shears. I used a third weight placed much closer to the balance rail to bring the keys to the final weight, but positioned them individually to make up for the differences from the widths of the keys.
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