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My keyboard was pushing 70-75grams in touch weight. It was high enough to start hurting my hands. Before hurt became injury I asked my RPT what could be done. He said plainly, "Your Renner Blue hammers are too damn heavy, shave them, they'll get bright, then re-voice them!"

Having had bad experiences with voicing bright hammers I said "No freaking way will you touch these hammers! I read something on Piano World about changing the leverage by slicing the balance rail punchings in half." He replied the results of that are variable and he wouldn't guarantee it would work. Then I said "I also read on Piano World that you can move the capstans and increase the leverage that way." He replied, "Yes, but YMMV, won't guarantee it."

He took the action to his shop and cut the punchings. When done he re-leveled the keys, adjusted the after-touch and reset the hammer drop. Unexpectedly he also had to adjust the side-to-side gap on some of the keys. I had said No Voicing but the notes at the bass-tenor break were whacky. He agreed, I found another couple out of whack and he needled them.

After this the touch weight fell to 55-60 grams and the key drop decreased by about a millimeter. It's a night & day difference in feel and playability. Even the voicing has changed because less force is driving the hammers into the strings? Not sure about that, but it's less bright, more mellow, more melodious across the board which I prefer.

I had hoped the balance rail punch cut would get the weight in the 65gram range so this is better than expected. He was surprised too at the weight drop. We agreed, no more mucking about for now.

I have to to thank the folks here because I never would've known to try this. So, "Thanks PW!"

Can you describe precisely what you mean by this expression: "changing the leverage by slicing the balance rail punchings in half."

I am having a hard time envisioning what this is, or how it helps.

This is an innovation that David Stanwood originated (I believe). The BR punching is glued (lightly) to the bottom of the key (in position). Then sliced in half parallel to the BR (front half removed). This moves the pivot point back a little towards the capstans, effectively increasing the leverage from the front of the key. It is intended as a reasonable alternative to redesign of the action such as moving capstans and/or altering knuckle placement, etc. Or as a diagnostic procedure.

Works quite well...as shown. Still, the techs warning...YMMV is true depending on the specifics of the action in question.

Pwg

I installed split balance rail punchings on my piano as well. It decreased the downweight dramatically without any adverse effects.

That's very interesting. Thanks for the explanations.

[edited as P W Grey had already answered this above}

Given the notable results reported above, this seems to present a wide range of adjustibility. One could choose 7/8 of a bushing for a little help, 3/4 of a bushing for a more notable gain in leverage, and 1/2 for maximum benefit.

Does the half bushing technique ever result in the bare bottom of the keystick making un-cushioned contact with the front edge of the balance rail, and any corresponding click or other noise?

No adverse effects whatsoever in my kbd (renner btw). They keys do have to be re-leveled and the key drop did decrease. For a heavy kbd this is a no brainer.

This is good to hear. My Kawai RX6 is not as terribly heavy as some pianos I've seen mentioned, but I find it too heavy for my preference. I measured near 60g in the middle of the keyboard, and 62-ish farther down. As a quick test, I had a tech take out one key, make sure it was fairly well-regulated and lubed, and then I compared it to the adjacent keys. I really couldn't detect much difference. I re-measured DW on that key, and it's still the same as the one next to it (about 57.5 g in this case).

Middle C measures about 60 DW / 37.5 UW, so friction doesn't seem to be too much of an issue. All the other suggestions to fix this are fairly complex and expensive, but I did have one tech recommend trying this punching-cutting technique. I even got a hold of Stanwood, and he thought it could help. I figure I'm going to try it and see. Since it's totally reversible, I don't see any harm.

Another suggestion was to reweight/rebalance the entire keyboard with lead weights, which would be thousands of dollars. Most people I've asked strongly discouraged doing that.