Grand Regulation: Key Dip - Part 3

Grand Regulation: Key Dip - Part 3

One role key dip should not play in a grand regulation is Keyframe Transfer Gauge.

Dip as Articulator and dip as Mediator work effectively on behalf of piano player enjoyment. With a firm cushion of frontrail punchings and a suitable aftertouch, dip provides consistency and comfort, control and finesse.

But the same dip falls short as a Keyframe Transfer Gauge. For 300 years, we piano technicians have suffered annoyance and lost time from dip being close but not close enough for setting up on a bench. And the cycles of work done extra times do not enhance our enjoyment! 

A WNG Portable Piano Pounder stabilizes compressibles, helping them stay as-adjusted longer. Settling parts glissandi-style as you regulate works well, too. But however stabilized we make them, frontrail punchings need to cushion as well as stop. A cloth punching traps air in its weave to be expelled and sucked back as the key is played. This makes dip comfortable for the player (and reduces noise) but it also makes dip pressure-sensitive as a measurement.

The thinnest frontrail punching is only .003” thin because soft punching compression undermines finer increments. Cardboard punchings do, too - they are just not flat enough or dense enough and they trap air between them, making their stack pressure-sensitive. Try replacing the soft punching with cardboard and test dip with a depth gauge.

Other factors also undermine a more accurate key dip. As noted in Key Dip – Part 2, if the key being measured is low (or high) compared to its neighbors, actual dip will be less (or more) when set with a dip block. Dip measuring, then, is key-level sensitive. And with key button wear or a twist in the keystick, a key squared at rest can be tilted at full dip, making key dip measuring wear-and-twist sensitive, too.

A WNG Dip Tool reduces compression-related inconsistencies with its substantial, self-positioning weight. And using aftertouch to tweak dip eliminates dip block errors. But aftertouch, being compression-sensitive, still has a tolerance of at least .003”. Although a machinist will charge good money to hold to such a tolerance, aspects of our work require greater precision.

In keyframe bedding, for instance, a .003” gap means action instability and noise, and action instability is a disqualifier for setting up to regulate on a bench. Good keyframe bedding in the piano (considered in future articles) eliminates spaces, opening up the possibility of accurate, on-bench regulating.

What, then, can replace dip as the Keyframe Transfer Gauge to produce accurate bench setups? And why are accurate bench setups important?

With a bench setup that matches the piano, key leveling can be done on the bench – and squaring and spacing and key dip. Regulation samples can be set up to head off wish-I-had-a, late-in-the-game realizations that are costly and disheartening. We can try out parts and materials early on instead and choose best solutions by trial and error in good light and with 360 degree access.

An accurate bench setup means you don’t have to go back and forth to the piano. And when you go to install the action, it fits. Meanwhile, saved time can be invested in details that make a difference.

Working away from the piano can benefit both owner and technician. And knowing the work can be performed predictably makes pricing easier and selling the work less financially hazardous.

But mostly, regulating with best-light visibility, less in the way, and less distraction make accurately going to the bench sweet.

When an action sits at rest in its piano, each key (whether at spec or not) touches backrail and balancerail but not frontrail. And at full dip, each key touches balancerail and frontrail but not backrail. In both cases, all three rails are not gauged by the key.

A solid (height-adjustable) device, however, that just fills the space between keystick and frontrail would allow for a go/no go process of tapping/not tapping to validate and have the space between key and frontrail named without a number - at an accuracy comparable to the frontrail-to-keybed fit, for which we also tap.

I have developed such a device, the Keystep. Like the WNG Dip Tool, it is height-adjustable and self-positioning. What you set it to in the piano is precisely what you fit with on the bench. The Keystep memorizes the space between key and frontrail, eliminating compression error by eliminating punchings and neutralizing wear-twist error by same-spot positioning. When the Keystep just connects key-at-rest with frontrail, the key touches all three rails simultaneously and becomes the Keyframe Transfer Gauge we need to move successfully to the bench!

In the next article, I will discuss letoff and drop roles in grand regulating.


John W. Keane

Thank you for writing these Chris! You’re the Stephen Hawking of piano tech work. Us mere mortals huff and puff while rubbing our eyes… 👍🎹🎸🤓🦆

John W. Keane

I have always replaced the front rail punchings (the ones I use to transfer the action to the bench) with cardboard (to the approx. thickness of the front rail cloth punching) to eliminate the elusive squish.


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