WNG Dip Tool measuring the dip of a natural key relative to its neighbors.

Grand Regulation: Key Dip - Part 2

Key dip, the Articulator, specifies a note’s depth of stroke and resulting hammer rise. Along with blow distance, letoff, and other geometry, it fine-tunes aftertouch, the follow-through needed for good and comfortable execution of each note. It also lifts the backcheck to its work and the damper to clear its strings. 

Depth of stroke (dip) as a measurement relates to neighboring keys. But the depth of stroke needed to produce a specific hammer rise and aftertouch is a distance traveled, irrespective of neighbors. So, when we use a dip block or a WNG Dip Tool to set dip, our keys need to be level for our dip to be accurate.

How level do they need to be?

What if the key being measured is a white balance punching low compared to its neighbors? .003” lower at the balance pin reduces key height by .006” at the key’s front. But a dip block doesn't account for a key starting .006” lower than the neighbors, so that dip as a distance will fall short by .006”, producing an aftertouch that is short by .030” (5 x .006” - nearly 1/32”). Even though the dip was accurately measured by the dip block, a correction of .006” will be needed - 2 white front punchings removed (2 x .003”) or 1 blue removed, 1 white added back (.009” - .003”) - to return aftertouch to where it would have been if the key had been level with its neighbors. This is dip back in the role of Mediator – we compensate for a key level error by adjusting dip.

If a player’s fingers are dancers, the keyboard’s dips are the dance floor. It may be more important to the player to have even aftertouch, but the dance will go smoother if the dance floor is also even.

Of course, if hammerline is uneven, that will affect aftertouch. And if letoff or drop is uneven, that will affect aftertouch. Each of these errors asks dip, the Mediator to step in and modify the aftertouch answer. Such modifications do help and there is a practical argument for using dip, the Mediator to improve the playability of a piano with regulation errors. In Part 1, I described a piano ridiculously out of regulation that was made playable in a short time, partly by shimming the balancerail to increase the entire keyboard’s dip.

In the case of a carefully regulated action, dip, the Articulator can raise the accuracy bar by insisting that measuring and actual distance equal each other. This pro-active troubleshooting device will find inconsistencies in key level, blow, letoff, and drop that can then be articulated or mediated depending on resources.

But how do we arrive at optimal dip and what is the best way to set it?

The piano maker’s specification, recommended as a simple number (3/8”, .390”, or 10mm), may or may not work easily with what else is there. A dip block or a spec presents a fixed solution to a complex set of inter-relationships. Anything between .375” and .425” might feel acceptable to a player, depending on other factors. But how movable are those other factors, and how acceptable? A shorter blow distance, for instance? Or an expensive altering of geometry?

Working to accurate string heights, letoff, drop, hammer line, and jack position empowers an accurate key dip to articulate the feel and control of a note from starting the key in motion through aftertouch to full dip and back. Each of these elements must be consistent and appropriate from note to note for an action's potential to be realized. And the keyframe must be well-supported – unstable rail heights destabilize key heights and respective dips.

So, the keyframe must be well-bedded in the piano and accurately supported on the bench. Underlifted strings should be nudged into the stable zone and strike accurately set up on the bench. Lack of access and impaired visibility compromise adjustments in the piano but insufficient precision in keyframe support and strike setup will compromise them on the bench. These factors require their own discussions later, but within the tolerance of what we can observe, there are numerous constraints that we can assess, consider, and judge to arrive at a successful result.

Blow distance shorter than 1.75” will adversely diminish power and blow distance over 1.75”, for most actions, will adversely diminish aftertouch and repetition. Sharp height above .500" stresses and trips up the player and sharp height less than .470” buries the sharp at dip, also tripping up the player. Too little aftertouch impedes a jack from clearing its knuckle after letoff and too much aftertouch may jam the jack into the end of its repetition lever. Each key must have enough front pin in the front bushings and enough balance pin clearing the balance bushings for stability. The action must fit the case parts with keyframe starting close enough to the bass cheek block for soft pedaling to have adequate clearance at the treble cheek block. Hammershanks must clear their rest cushions but not be so high above them that rear under-shoulders of the hammers are not stopped from bumping on top of the backchecks. Backchecks must reach tails at a suitable checking height with tails not scraping backchecks on hard blows. Drop screws must fit under the pinblock. Jacks cannot cheat out from under knuckles on hard blows. No sides of parts should rub against each other. Downweight need not be above 54 grams and upweight must never go below 20 grams. And so forth.

These are practical specs. Specs that can be tested by running samples and specs that need compliance for the piano to be enjoyably playable.

From the day a piano is born, the geometry is in motion. Hammers wear, rest cushions and punchings compress. Original specs are left behind for relationships of the moment. In a well-designed action, self-compensation mitigates. Front punchings compress but balance punchings also compress. And simple touch-ups of blow distance and letoff cure symptoms of knuckle, letoff button cloth, and backrail cloth compression. 

If materials or parts are changed, they almost certainly will not be dimensionally identical to the originals. Take replacement hammershanks. Heyday Steinway knuckles were 9mm in diameter but 10mm tall. Modern shanks have 9mm or 10mm knuckles that are 9mm or 10mm tall respectively. The angle of address jack-to-knuckle changes with a change of knuckle “tallness”. So, we have an unsatisfactory choice of 9mm height bringing aftertouch back toward the rep lever’s felt stop or the clearance needed for a 10mm knuckle bringing aftertouch back toward the rep lever’s felt stop. Both increase the chances of jacks jamming toward the end of aftertouch. Aftertouch should land the finger’s power comfortably on a soft front punching (with a little wiggle left at the jack tender). Dip being stopped in the rep lever is a potential hazard of mixing old and new parts. And new whippens may not improve the situation.

Action relationships are a movable feast best served with flexibility and acknowledgement. A spec or a dip block, ultimately, is too shallow a solution. By running samples (accurate samples) early in the regulation, the real situation can be observed. If compliance with the practical specs is violated, a geometry change will be needed. The simplest will be to reconsider parts and materials. Other solutions could involve moving rail heights or spacing, moving knuckles or capstans, changing hammer bore or where hammers are hung. The choices range from easy to impossible and each choice comes with collateral effects on other elements.

In the end, setting dip by aftertouch (or setting aftertouch by dip) is the fastest and most useful way to best results. It naturally integrates sharps with naturals. Results, of course, improve with accurate key level, hammerline, jack position, letoff, and drop – and consistency of friction, inertia, and spring tension – all the details. But results will be acceptable if aftertouch is adequate and even. And tweaking dip is the most direct way of tweaking aftertouch.

Ironically, the action with good geometry will be the most forgiving in terms of accuracy. Conversely, if jacks in an action setup are just beginning to jam at fullest dip, then the dip better be very even (or left too shallow).

But the upside of out-of-compliance actions is that we can make a huge difference to their playability, while charging well for our work and delighting the customer with results that exceed expectation. Run samples, pay attention, and make assessments early on. Then, depending on depth of resources and objectives of customer, use dip, the Mediator or dip, the Articulator to best regulate the action.


Dale Erwin

Use an Erwin dip gauge :)

Dale Erwin
Gary Bruce

Hi Chris. Thanks for the thorough article. I appreciate your dedication to quality work and we’re using our regulation station regularly with great results.

Gary Bruce
Norm Radford

Chris, as always, a fine article! Well explained, while leaving room for further exploration and research. A great reference! I always receive a superb benefit from your great knowledge.

Norm Radford
John W. Keane

👍🎹🤓🦆 Nicely “articulated”, Chris!

John W. Keane
David Hughes

And though you mention this towards the end, it goes without saying the the hammer bore distance must be correct from the get-go. All the screw turning and punching tweaking will not rescue us from hammers that were improperly bored to the string heights, especially those that are too short. Great job, Chris. Eloquent, thorough, and technically spot on.

David Hughes
Debbie Cyr

Really well written, thoughtful and thought provoking article!

Debbie Cyr

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