Pianotech

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

The most complete answer to your question is contained in a really great article written by Jason Cassel in the November 2025 issue of the Journal.  Read all the way to the end for the "ah-ha" moment you're looking for.

------------------------------
Daniel DeBiasio
Technical Education & Support
ddebiasio@steinway.com
718-267-3229
Steinway & Sons

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

Thanks everyone for your insights!

To answer your question David, and this also relates to the article you cited, Daniel – and thanks for directing me to it, as I've been behind on reading the Journal.

I've had trouble getting enough drop after establishing simultaneous escapement, on more than one action.  Perhaps I'm not properly unlocking the three padlocks, or there are complications with worn action parts.  But exploring the issue caused me to stumble across a parameter I haven't ever heard discussed.

I am coming to believe that the behavior of drop, within the scope of simultaneous escapement, can (and perhaps, should) be manipulated.  I've realized that, while maintaining simultaneous escapement, the distance of drop that occurs is related to the distance the jack must travel to fully release the knuckle.  Or rather, simultaneous escapement must occur sooner when the jack toe hits its button sooner, which is what occurs when the jack is positioned further under the knuckle.  This results in a greater difference in hammer position at let off vs drop (again, while maintaining sim. esc.).

In the same spirit of setting regulation adjustments based upon interactions and behaviors rather than specs and gauges, as Jason puts forth in the aforementioned article...
Aside from the problem of sometimes having not enough drop across the whole action, I've also observed differences in drop between notes, even on actions that do have enough drop. Some notes I'd like to increase, and other's I'd like to decrease just a little bit, but I don't want to mess up the simultaneous escapement.  This discrepancy in drop behavior, I think, is the result of inconsistent jack vs knuckle behavior.  Not all knuckles are created the same.  We have been setting jack position based on a visual alignment, but this can result in inconsistent drop behavior.  So… jack-knuckle alignment could (should!) be based upon creating consistent and proper drop, rather than entirely based on what position it appears to be sitting beneath the knuckle core.  (Again, this is entirely based upon maintaining simultaneous escapement.)

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-29-2026 15:04
From: Daniel DeBiasio
Subject: Jack-to-knuckle alignment question

The most complete answer to your question is contained in a really great article written by Jason Cassel in the November 2025 issue of the Journal.  Read all the way to the end for the "ah-ha" moment you're looking for.

------------------------------
Daniel DeBiasio
Technical Education & Support
ddebiasio@steinway.com
718-267-3229
Steinway & Sons

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

You might try the article 

Action Spread... What's all the Hubbub? By Jim Ialeggio, Piano Technicians Journal / April 2019

Thanks everyone for your insights!

To answer your question David, and this also relates to the article you cited, Daniel – and thanks for directing me to it, as I've been behind on reading the Journal.

I've had trouble getting enough drop after establishing simultaneous escapement, on more than one action.  Perhaps I'm not properly unlocking the three padlocks, or there are complications with worn action parts.  But exploring the issue caused me to stumble across a parameter I haven't ever heard discussed.

I am coming to believe that the behavior of drop, within the scope of simultaneous escapement, can (and perhaps, should) be manipulated.  I've realized that, while maintaining simultaneous escapement, the distance of drop that occurs is related to the distance the jack must travel to fully release the knuckle.  Or rather, simultaneous escapement must occur sooner when the jack toe hits its button sooner, which is what occurs when the jack is positioned further under the knuckle.  This results in a greater difference in hammer position at let off vs drop (again, while maintaining sim. esc.).

In the same spirit of setting regulation adjustments based upon interactions and behaviors rather than specs and gauges, as Jason puts forth in the aforementioned article...
Aside from the problem of sometimes having not enough drop across the whole action, I've also observed differences in drop between notes, even on actions that do have enough drop. Some notes I'd like to increase, and other's I'd like to decrease just a little bit, but I don't want to mess up the simultaneous escapement.  This discrepancy in drop behavior, I think, is the result of inconsistent jack vs knuckle behavior.  Not all knuckles are created the same.  We have been setting jack position based on a visual alignment, but this can result in inconsistent drop behavior.  So… jack-knuckle alignment could (should!) be based upon creating consistent and proper drop, rather than entirely based on what position it appears to be sitting beneath the knuckle core.  (Again, this is entirely based upon maintaining simultaneous escapement.)

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-29-2026 15:04
From: Daniel DeBiasio
Subject: Jack-to-knuckle alignment question

The most complete answer to your question is contained in a really great article written by Jason Cassel in the November 2025 issue of the Journal.  Read all the way to the end for the "ah-ha" moment you're looking for.

------------------------------
Daniel DeBiasio
Technical Education & Support
ddebiasio@steinway.com
718-267-3229
Steinway & Sons

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

Agreed.  Because it takes longer distance of key travel between the start and end of the knuckle's release, the player will feel that bump sooner in the dip.  Whether or not friction actually does increase a significant amount, the player likely would perceive a heavier touch.

But you're right, with the minimal experimenting I've done, it seems that 1mm further behind the knuckle is the upper limit needed to get the change I'm seeking. And to that point... if a fraction of a mm makes a significant difference, we can expect that visual alignment leaves plenty of room for error.

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

So... what we should be doing is asking our better players to test their piano before and after we reset the jack to knuckle distance both forward and back and see if they can feel a difference or have a preference.  It doesn't have to be the entire piano, perhaps just a middle octave to see an effect.

My bet is that there would be an effect, but the player won't be able to determine their preference or they would just be guessing.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-30-2026 10:30
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Agreed.  Because it takes longer distance of key travel between the start and end of the knuckle's release, the player will feel that bump sooner in the dip.  Whether or not friction actually does increase a significant amount, the player likely would perceive a heavier touch.

But you're right, with the minimal experimenting I've done, it seems that 1mm further behind the knuckle is the upper limit needed to get the change I'm seeking. And to that point... if a fraction of a mm makes a significant difference, we can expect that visual alignment leaves plenty of room for error.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 04:06
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

I would like to perform that test.  Perhaps that's what I should have done before flapping my mouth!  I'll try to determine a delta for the max spread of letoff range. And maybe that could help measure something of a player's touch sensitivity.

It seems like there isn't an established functional reason to align the jack and knuckle core rears to be flush.  Putting aside the potential for some difference in touch – the most compelling reasons seem to be: having a target for where to place it, and "we've always done it this way and it makes sense".  

Anyone out there willing to disagree?

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 21:10
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

So... what we should be doing is asking our better players to test their piano before and after we reset the jack to knuckle distance both forward and back and see if they can feel a difference or have a preference.  It doesn't have to be the entire piano, perhaps just a middle octave to see an effect.

My bet is that there would be an effect, but the player won't be able to determine their preference or they would just be guessing.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-30-2026 10:30
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Agreed.  Because it takes longer distance of key travel between the start and end of the knuckle's release, the player will feel that bump sooner in the dip.  Whether or not friction actually does increase a significant amount, the player likely would perceive a heavier touch.

But you're right, with the minimal experimenting I've done, it seems that 1mm further behind the knuckle is the upper limit needed to get the change I'm seeking. And to that point... if a fraction of a mm makes a significant difference, we can expect that visual alignment leaves plenty of room for error.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 04:06
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

Robin, regarding an established function. It seems to me that when the jack is aligned with the core, the surface area of the jack will steadily diminish as it makes its transit. If it is set behind the core, the surface area will momentarily increase and then decrease after it passes the alignment with the core. Theoretically this could be felt by the player. I suppose the condition of the knuckle comes into play here, the intent is for a rounded knuckle, not a flat one.

------------------------------
Steven Rosenthal RPT
Honolulu HI
(808) 521-7129

Original Message:
Sent: 01-31-2026 08:33
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

I would like to perform that test.  Perhaps that's what I should have done before flapping my mouth!  I'll try to determine a delta for the max spread of letoff range. And maybe that could help measure something of a player's touch sensitivity.

It seems like there isn't an established functional reason to align the jack and knuckle core rears to be flush.  Putting aside the potential for some difference in touch – the most compelling reasons seem to be: having a target for where to place it, and "we've always done it this way and it makes sense".  

Anyone out there willing to disagree?

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 21:10
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

So... what we should be doing is asking our better players to test their piano before and after we reset the jack to knuckle distance both forward and back and see if they can feel a difference or have a preference.  It doesn't have to be the entire piano, perhaps just a middle octave to see an effect.

My bet is that there would be an effect, but the player won't be able to determine their preference or they would just be guessing.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-30-2026 10:30
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Agreed.  Because it takes longer distance of key travel between the start and end of the knuckle's release, the player will feel that bump sooner in the dip.  Whether or not friction actually does increase a significant amount, the player likely would perceive a heavier touch.

But you're right, with the minimal experimenting I've done, it seems that 1mm further behind the knuckle is the upper limit needed to get the change I'm seeking. And to that point... if a fraction of a mm makes a significant difference, we can expect that visual alignment leaves plenty of room for error.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 04:06
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

Robin, regarding an established function. It seems to me that when the jack is aligned with the core, the surface area of the jack will steadily diminish as it makes its transit. If it is set behind the core, the surface area will momentarily increase and then decrease after it passes the alignment with the core. Theoretically this could be felt by the player. I suppose the condition of the knuckle comes into play here, the intent is for a rounded knuckle, not a flat one.

------------------------------
Steven Rosenthal RPT
Honolulu HI
(808) 521-7129

Original Message:
Sent: 01-31-2026 08:33
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

I would like to perform that test.  Perhaps that's what I should have done before flapping my mouth!  I'll try to determine a delta for the max spread of letoff range. And maybe that could help measure something of a player's touch sensitivity.

It seems like there isn't an established functional reason to align the jack and knuckle core rears to be flush.  Putting aside the potential for some difference in touch – the most compelling reasons seem to be: having a target for where to place it, and "we've always done it this way and it makes sense".  

Anyone out there willing to disagree?

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 21:10
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

So... what we should be doing is asking our better players to test their piano before and after we reset the jack to knuckle distance both forward and back and see if they can feel a difference or have a preference.  It doesn't have to be the entire piano, perhaps just a middle octave to see an effect.

My bet is that there would be an effect, but the player won't be able to determine their preference or they would just be guessing.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-30-2026 10:30
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Agreed.  Because it takes longer distance of key travel between the start and end of the knuckle's release, the player will feel that bump sooner in the dip.  Whether or not friction actually does increase a significant amount, the player likely would perceive a heavier touch.

But you're right, with the minimal experimenting I've done, it seems that 1mm further behind the knuckle is the upper limit needed to get the change I'm seeking. And to that point... if a fraction of a mm makes a significant difference, we can expect that visual alignment leaves plenty of room for error.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-30-2026 04:06
From: Blaine Hebert
Subject: Jack-to-knuckle alignment question

It seems to me that moving the jack further back under the knuckle might slightly increase resistance and perhaps power, while moving it further out might increase speed and lighten touch.  But I might also guess that the required amounts of movement would be in the order of small fractions of a mm.

I need to review Jim Ialeggio, Piano Technicians Journal / April 2019 and the Jason Cassel article in the November 2025 issue.

------------------------------
Blaine Hebert RPT
Duarte CA
(626) 390-0512

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

It's a good question.  I do believe that this adjustment is under ideal conditions, and mostly "it just works".  On some Baldwin grands (the old American models), I would regularly find the hammers "cheating" and losing power, and the only cure was setting the jacks further under the knuckle.  The test is to hold down the hammer while pushing down on the key through the key stroke.  You can easily tell if there's cheating going on.  I don't claim to know why this is, specific to those Baldwins.  Maybe it's the nap of the buckskin is in a different direction.  Who knows.  The main thing is, it's just got to work.  Flat knuckles changes a lot in the regulation process, and friction there will affect the touch if the jack is too far under the knuckle.  Lubrication there can also affect the regulation because your rep spring also gets involved, and sometimes lubing the knuckles and wippens will reveal that the rep spring is too strong.

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

Thanks for your thoughts about this, Paul.  I just did a little experiment, with reply about in an above comment.  I noticed that this Baldwin has angled jack tops.  Perhaps that influenced the hammers cheating out that you experienced?  I'm also going to keep in mind what you said about the buckskin nap when I do more experimenting.

I was actually trying to see if the rep spring had any influence over my "not getting enough drop with double escapement" problem, so I'll do some testing with lubing the knuckles and other parts, and perhaps it's a good idea to also test high and low frictions on the rep lever pinning.  Thanks for the perspective!

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201

Original Message:
Sent: 01-31-2026 09:16
From: Paul McCloud
Subject: Jack-to-knuckle alignment question

It's a good question.  I do believe that this adjustment is under ideal conditions, and mostly "it just works".  On some Baldwin grands (the old American models), I would regularly find the hammers "cheating" and losing power, and the only cure was setting the jacks further under the knuckle.  The test is to hold down the hammer while pushing down on the key through the key stroke.  You can easily tell if there's cheating going on.  I don't claim to know why this is, specific to those Baldwins.  Maybe it's the nap of the buckskin is in a different direction.  Who knows.  The main thing is, it's just got to work.  Flat knuckles changes a lot in the regulation process, and friction there will affect the touch if the jack is too far under the knuckle.  Lubrication there can also affect the regulation because your rep spring also gets involved, and sometimes lubing the knuckles and wippens will reveal that the rep spring is too strong.

------------------------------
Paul McCloud, RPT
Accutone Piano Service
www.AccutonePianoService.com
pavadasa@gmail.com

Original Message:
Sent: 01-29-2026 13:49
From: Robin Whitehouse
Subject: Jack-to-knuckle alignment question

Can anyone give an explanation for why the jack and knuckle should be aligned at the rear edge, and not further under the jack?  

If going shallower under the knuckle, it will of course cheat out, trip early, lose power, etc.  But I don't recall ever hearing a reason that the jack couldn't be positioned deeper under the knuckle core – assuming that other operations are not impeded when doing so.

------------------------------
Robin Whitehouse
Greenbelt, MD
D.C. Chapter 201
------------------------------