Pianotech

Terry Farrell (Post #4),

In my opinion (and what do I know, really), a Steinway bridge root/trunk (as one example) is made to the "ideal" height at the factory. This vertically laminated member is strong/unyielding in its original height from end to end, with a cap glued atop that is just tall enough to accommodate the deepest union notches. If we reduce the root to accommodate a thicker cap, we weaken it. The cap material is flexible in its linear dimension; the bridge root is not, and there's a reason for that. The root supports the crown along the grain of the soundboard for the life of the instrument. In my rebuilding work, and again what the heck do I know, I never violated the height of the root. I was much happier "wasting" cap material than reducing the root. I know you use a vertically laminated cap, and perhaps this makes up for the loss (but you have introduced a glue joint that never existed at that elevation, and the root structure would be stronger without it, with continuous vertical grain top-to-bottom, methinks), but I have seen scads of rebuilt Steinway and Mason & Hamlin pianos over the last 45 years with significantly reduced roots and chunky quartersawn maple caps, and they distress me.

David G. Hughes, RPT

Baltimore Chapter

I know very little about bellyman work, but I know that the net outcome of the bridge downbearing is essential to the sound quality: volume, sustain, thinness/weakness, tone, etc with particular sensitivity in the treble. A certain number of the rebuilt grands that I come across, in homes and in stores, have portions of their treble with deficiencies in sound. If I am right in this observation, then what is the probability of success for a typical rebuild?

Your post, David, seems straight-forward for setting the downbearing (in an overall complex process!) before beginning to restring. Is the object to achieve an equal downbearing across the whole scale when you are done restringing, as measured by angle? Or if, as I assume, the (real) target is equality as measured by string downward pressure/force, how many pounds per string do you target for? 

Finally, I have the impression that the physical downbearing (of strings pushing on the bridges) is non-linear across the complete scale. If this is the case, do you somehow have to pre-load against the bridges (when shaping the bridges) to garner your desired downbearing end result after restringing?

Regards, Norman. 

Terry Farrell (Post #4),

In my opinion (and what do I know, really), a Steinway bridge root/trunk (as one example) is made to the "ideal" height at the factory. This vertically laminated member is strong/unyielding in its original height from end to end, with a cap glued atop that is just tall enough to accommodate the deepest union notches. If we reduce the root to accommodate a thicker cap, we weaken it. The cap material is flexible in its linear dimension; the bridge root is not, and there's a reason for that. The root supports the crown along the grain of the soundboard for the life of the instrument. In my rebuilding work, and again what the heck do I know, I never violated the height of the root. I was much happier "wasting" cap material than reducing the root. I know you use a vertically laminated cap, and perhaps this makes up for the loss (but you have introduced a glue joint that never existed at that elevation, and the root structure would be stronger without it, with continuous vertical grain top-to-bottom, methinks), but I have seen scads of rebuilt Steinway and Mason & Hamlin pianos over the last 45 years with significantly reduced roots and chunky quartersawn maple caps, and they distress me.

David G. Hughes, RPT

Baltimore Chapter

The bridges participation of the tonal characteristic can easily be underestimated. Years ago i visited the shop of another technician struggling with this very issue. It was a 7' Chickering I believe with a very narrow bridge for a piano that size. The technician had lowered the tension of the strings, and removed all of the coils off the pins, removed the strings off the bridges, and had the plate up in the air. When i walked in he was adding a bridge boot for stiffness and mass. I remember thinking at the time that just listening to the piano before tear down probably would have save a lot of time. So he was dealing with too open a sound. The opposite happens with too much stiffness, That's why i never use laminated caps and stay close to the original design.

-chris

I know very little about bellyman work, but I know that the net outcome of the bridge downbearing is essential to the sound quality: volume, sustain, thinness/weakness, tone, etc with particular sensitivity in the treble. A certain number of the rebuilt grands that I come across, in homes and in stores, have portions of their treble with deficiencies in sound. If I am right in this observation, then what is the probability of success for a typical rebuild?

Your post, David, seems straight-forward for setting the downbearing (in an overall complex process!) before beginning to restring. Is the object to achieve an equal downbearing across the whole scale when you are done restringing, as measured by angle? Or if, as I assume, the (real) target is equality as measured by string downward pressure/force, how many pounds per string do you target for? 

Finally, I have the impression that the physical downbearing (of strings pushing on the bridges) is non-linear across the complete scale. If this is the case, do you somehow have to pre-load against the bridges (when shaping the bridges) to garner your desired downbearing end result after restringing?

Regards, Norman. 

Terry Farrell (Post #4),

In my opinion (and what do I know, really), a Steinway bridge root/trunk (as one example) is made to the "ideal" height at the factory. This vertically laminated member is strong/unyielding in its original height from end to end, with a cap glued atop that is just tall enough to accommodate the deepest union notches. If we reduce the root to accommodate a thicker cap, we weaken it. The cap material is flexible in its linear dimension; the bridge root is not, and there's a reason for that. The root supports the crown along the grain of the soundboard for the life of the instrument. In my rebuilding work, and again what the heck do I know, I never violated the height of the root. I was much happier "wasting" cap material than reducing the root. I know you use a vertically laminated cap, and perhaps this makes up for the loss (but you have introduced a glue joint that never existed at that elevation, and the root structure would be stronger without it, with continuous vertical grain top-to-bottom, methinks), but I have seen scads of rebuilt Steinway and Mason & Hamlin pianos over the last 45 years with significantly reduced roots and chunky quartersawn maple caps, and they distress me.

David G. Hughes, RPT

Baltimore Chapter

I know very little about bellyman work, but I know that the net outcome of the bridge downbearing is essential to the sound quality: volume, sustain, thinness/weakness, tone, etc with particular sensitivity in the treble. A certain number of the rebuilt grands that I come across, in homes and in stores, have portions of their treble with deficiencies in sound. If I am right in this observation, then what is the probability of success for a typical rebuild?

Your post, David, seems straight-forward for setting the downbearing (in an overall complex process!) before beginning to restring. Is the object to achieve an equal downbearing across the whole scale when you are done restringing, as measured by angle? Or if, as I assume, the (real) target is equality as measured by string downward pressure/force, how many pounds per string do you target for? 

Finally, I have the impression that the physical downbearing (of strings pushing on the bridges) is non-linear across the complete scale. If this is the case, do you somehow have to pre-load against the bridges (when shaping the bridges) to garner your desired downbearing end result after restringing?

Regards, Norman. 

Terry Farrell (Post #4),

In my opinion (and what do I know, really), a Steinway bridge root/trunk (as one example) is made to the "ideal" height at the factory. This vertically laminated member is strong/unyielding in its original height from end to end, with a cap glued atop that is just tall enough to accommodate the deepest union notches. If we reduce the root to accommodate a thicker cap, we weaken it. The cap material is flexible in its linear dimension; the bridge root is not, and there's a reason for that. The root supports the crown along the grain of the soundboard for the life of the instrument. In my rebuilding work, and again what the heck do I know, I never violated the height of the root. I was much happier "wasting" cap material than reducing the root. I know you use a vertically laminated cap, and perhaps this makes up for the loss (but you have introduced a glue joint that never existed at that elevation, and the root structure would be stronger without it, with continuous vertical grain top-to-bottom, methinks), but I have seen scads of rebuilt Steinway and Mason & Hamlin pianos over the last 45 years with significantly reduced roots and chunky quartersawn maple caps, and they distress me.

David G. Hughes, RPT

Baltimore Chapter

Norman

Those are all good questions and there are different answers as people take different approaches.  What I posted was just a method of determining the thickness of the new cap in advance of gluing it on.  That's all.  The other questions you ask or much more complicated but worthy of discussion.  They also  require a longer response which I will provide but it will take some time to draft.  In the meantime, I would recommend that everyone read Nick Gravagne's excellent series on downbearing that starts in the 1988 PTJ (February) and runs, I believe, through November of that year.  Many of these questions are addressed, or alluded to.  

Some of the questions are:

1. How many degrees of downbearing should be set in each part of the scale (there are different attitudes about that).  Should we target equal bearing across the scale?  If not, then what?  
2. What, if any difference should there be in along the long bridge versus that bass bridge
3. What about downbearing on older soundboards?
4. How does available crown affect our DB choices?
5. Are the deficiencies you refer to a product of downbearing or are there other factors that might be contributing (hammer characteristics, e.g.)?
6. Does per string downbearing measured after the piano is pulled to pitch actually indicate the load that falls right below that string on the SB?
7. Forces coming from DB are vector forces.  Are those forces always 90 degrees to the SB or are vector forces transmitted in other directions, say along the ribs
8. What kind of residual bearing should we target or expect and what does that mean in terms of our original, pre-tension downbearing settings?
9. The soundboard reacting as a compressed spring is "non-linear", as you mention, so what does that mean in this context and is it important?
10. Should we pre-stress the board before we set bearing, why and how?

I'll come back to those questions but I need a bit more time than I have this morning.  Of course, others can weigh in in the meantime, and, lol, I'm sure they will, for better or for worse.

------------------------------
David Love RPT
www.davidlovepianos.com
davidlovepianos@comcast.net
415 407 8320
------------------------------


Original Message:
Sent: 09-16-2025 11:17
From: Norman Brickman
Subject: Downbearing Bridge Cap Thickness Tool

I know very little about bellyman work, but I know that the net outcome of the bridge downbearing is essential to the sound quality: volume, sustain, thinness/weakness, tone, etc with particular sensitivity in the treble. A certain number of the rebuilt grands that I come across, in homes and in stores, have portions of their treble with deficiencies in sound. If I am right in this observation, then what is the probability of success for a typical rebuild?

Your post, David, seems straight-forward for setting the downbearing (in an overall complex process!) before beginning to restring. Is the object to achieve an equal downbearing across the whole scale when you are done restringing, as measured by angle? Or if, as I assume, the (real) target is equality as measured by string downward pressure/force, how many pounds per string do you target for? 

Finally, I have the impression that the physical downbearing (of strings pushing on the bridges) is non-linear across the complete scale. If this is the case, do you somehow have to pre-load against the bridges (when shaping the bridges) to garner your desired downbearing end result after restringing?

Regards, Norman. 

------------------------------
Norman Brickman
Potomac Piano Service
Potomac, Maryland
potomacpiano@verizon.net
https://potomacpiano.com
(301) 983.9321


Original Message:
Sent: 09-16-2025 09:53
From: David Hughes
Subject: Downbearing Bridge Cap Thickness Tool

Terry Farrell (Post #4),

In my opinion (and what do I know, really), a Steinway bridge root/trunk (as one example) is made to the "ideal" height at the factory. This vertically laminated member is strong/unyielding in its original height from end to end, with a cap glued atop that is just tall enough to accommodate the deepest union notches. If we reduce the root to accommodate a thicker cap, we weaken it. The cap material is flexible in its linear dimension; the bridge root is not, and there's a reason for that. The root supports the crown along the grain of the soundboard for the life of the instrument. In my rebuilding work, and again what the heck do I know, I never violated the height of the root. I was much happier "wasting" cap material than reducing the root. I know you use a vertically laminated cap, and perhaps this makes up for the loss (but you have introduced a glue joint that never existed at that elevation, and the root structure would be stronger without it, with continuous vertical grain top-to-bottom, methinks), but I have seen scads of rebuilt Steinway and Mason & Hamlin pianos over the last 45 years with significantly reduced roots and chunky quartersawn maple caps, and they distress me.

David G. Hughes, RPT

Baltimore Chapter

------------------------------
David Hughes RPT
Vintage Case Parts
Glyndon MD
(443) 522-2201


Original Message:
Sent: 09-16-2025 09:19
From: Terrence Farrell
Subject: Downbearing Bridge Cap Thickness Tool

That is very close to the way that I've always set my downbearing. The only difference in my method is that because I use laminated bridge caps and don't really want to be planing down the cap that I just made, what I do is use your method to plane down the bridge root so that after the uniform-thickness cap is added, I get the bridge height I want. When measuring the downbearing for root planing, I simply include a spacer the same thickness of the cap. This has always worked well for me.

Terry Farrell

So getting back to some of the questions in response to Norman's post.  But before I get into it, I have to respond to Chris's comments.  I think an honest discussion of downbearing procedures can bear fruit for everyone.  Chris's comments and criticisms are classic straw man fallacies (it gets tiring correcting the record, honestly).  For those who don't know what that is, it's a logical fallacy that involves misstating or misrepresenting someone's argument, or point, in order to make your argument.  It's a common error, when not a tactic. It doesn't contribute to advancing the discussion. I won't waste a lot of time with it but feel compelled to correct the record. 

First, suggesting that this leads to a 5 degree bearing angle is preposterous.  I've never had that happen and I've never even seen a 5 degree bearing angle on a Steinway of any age in spite of your stated flaws of Steinway processes (careful that might be libelous).  I did not discuss the entire procedure or doing this in a dry fit situation, which I don't do.  I cap and notch the bridge in the piano after the board is glued in with an uncapped bridge root.  I agree, not controlling moisture can be a problem. I doubt it ever leads to a 4 or 5 degree difference but it's certainly possible that it leads to some error.  I think it's best to set the bearing at the anticipated or desired final EMC/RH which is usually about 40 - 50% RH.  

Second, I never said that a 1 degree bearing angle was the target.  In fact, my distance bearing target when determining bridge cap thickness is 1.5 degrees on a prestressed board.  When tension is pulled to pitch I hope the residual bearing is around 1/2 of that, or .75 +/- degrees.  I also set the bearing on bass bridge after the tension is pulled up in the plain wire section and target between 0-.5 degrees (just like Chris whoopee!), but probably closer to .5.  Seems Chris missed an opportunity to agree on something.  

Third, Gravagne doesn't use the quarter-nickel-dime method (I'm pretty sure as we've discussed it).  In fact, in one of those articles he discusses the problems with that method and why it is not reliable!  For those interested, the quarter-nickel-dime method means you are using a quarter for your distance gauge in the low tenor, a nickel in the mid tenor and a dime in the treble.  The reason it's not reliable is that the distance bearing will depend on the length of the backscale.  If you want 1 degree of bearing then the math is to use the sine of the angle of 1 degree (.0175) times the length of the backscale.  That will give you the distance bearing over the rear string rest (see my original illustration).  A quarter is .060" thick.  Thus, multiply .0175* times the length of the backscale and that should equal .060".   So for .060" distance bearing the backscale would have to be ~3.42".  But what if the backscale is 8", as it is on many pianos (Steinway B for example)?  Then the distance bearing would have to be .0175 x 8 or .140"!  That's more than 2.3 times the thickness of a quarter.  (Just a note: my distance bearing setting on a new board is more like 1.5 degrees, the sine of which is ~.026.  So for an 8" backscale, if you wanted 1.5 degrees, you would need a distance bearing of .208", just under a 1/4" and 3.5 times the thickness of a quarter!). I think for Chris, maybe he might get more out of the articles if he read them more carefully and actually understood the details of their content.  I personally just reread them in advance of a DB presentation I was giving to the local chapter, a trial for a class I'm hoping to give later, and I got a lot out of them, including some new questions that didn't occur to me when I read them some 37 years ago.      

The original post was about a tool and its use, nothing more.  I didn't plan to outline my complete method of setting downbearing, bridge cap height or anything else other than show a picture of a tool I use for purposes of measuring and calculating (and it works).  I thought the information might be useful, I found the tool made things easier and more reliable for me.  I'm not selling anything.  I assumed those for whom I posted this were familiar with the process.  But for those who aren't, this is a good opportunity and I'm more than happy to contribute what I know.  If I don't know, I'll say so.  In the words of Oscar Wilde, "I'm not young enough to think I know everything".  

I'll get into answering Norman's questions in a separate post but not tonight.  They are good questions.

Norman

Those are all good questions and there are different answers as people take different approaches.  What I posted was just a method of determining the thickness of the new cap in advance of gluing it on.  That's all.  The other questions you ask or much more complicated but worthy of discussion.  They also  require a longer response which I will provide but it will