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Gapping between top of piinblock and underside of plate

  • 1.  Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 7 days ago

    I saw a piano (Steinway B) that is in process of being rebuilt.  PBlock and plate are installed; block has been drilled.  Plate is unusually thick in some areas.  Flange fitting is good but in  one section (first treble) there is gapping between top of block and underside of plate.  What are potential problems with regard to structural failure or stability, and, if warranted,  any potential solutions, short of replacing block.  I had thought about some sort of epoxy putty, but have no experience with this. 

     

    Thanks

     

    David Skolnik

     

     

     

     



  • 2.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 7 days ago
    David

    I'm trying to visualize this.  How can you tell that there is a gap between the block and bottom of the plate?  Are you talking in the front of the block, towards the stretcher, or the back of the block, against the plate flange?  If it's back, by the plate flange, how can you tell? If it's towards the back, would the plate screws pull the block up to the plate?

    And if you saw this in the process of being rebuilt, did you bring this to attention of the rebuilder?

    Just asking.

    ------------------------------
    Willem "Wim" Blees, RPT
    Mililani, HI 96789
    ------------------------------



  • 3.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 7 days ago
    Hi Wim -
    The area in question is neither the block/flange nor block/stretcher interface. Rather, it's between top face of block and underside of tuning pin webbing area.  It looked like it might have been due to some unevenness in the plate that allowed this one treble section to remain un-fitted.  It was easy enough to ascertain with bent-wire feeler as piano is as yet un-strung.  I have nothing to do with the piano and am likely not in a position to discuss this with rebuilder, one way or another, but I, too, was 'just wondering':
    - what potential structural and functional ramifications?
         - pinblock failure
         - plate failure
         - tuning instability
    - possible corrections (if warranted) short of block replacement?
         - shimming?
         - epoxy putty?
         -   ?

    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 4.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 7 days ago
    S&S tuning pin webbing is very rarely a flat plane...they can be pretty bowed, usually in the middle, I think. Others are also very rarely a flat plane. S&S has an overhead router setup to fit this top face to the specific plate. I do pay some attention to fitting the top face, but nowhere near as much attention as the flange. Epoxy can help if its way out of plane, if you drill for the pins in the piano.

    As far as what happens if the webbing is not tight to the top face of the block...with intermittent gaps, I don't think its an issue. Very large gaps...maybe but not even sure here if its an issue. The block wants to pull up near the stretcher, and rotate down near the flange. The flange is beveled to resist the downward rotational tendency, so that part is not effected by a terrible webbing fit. The stretcher end end of the block is restrained, to some degree by the glue joint of block to stretcher. If there is intermittent gaps, I would not sweat it. Gapping of the whole top face would be pretty hard to achieve, I think. That leaves intermittent , which I don't think is functionally a big deal.

    Open face blocks have no restraining webbing on the top face. Those pianos can be stable. Bechstein's open face tends to rotate down in the front, but that's because the flange is not beveled.

    I'm not sure its an issue




    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 5.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 7 days ago
    I was taught to fit the pinblock to both the flange and plate surface. The longest time is spent fitting the top surface and this also make the most dust.

    All Steinway plates bow in the middle. This means one must remove the most material from the treble end. If this block has space there, they had to work to put it there.

    On the last 10 or so blocks I have used a 4' level as a straight edge and I use a very coarse surface grinder to level the plate surface before fitting the block. Metal dust doesn't travel very far and the process takes less time.

































































    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------



  • 6.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 7 days ago
    Ed, how much metal are you comfortable removing?

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 7.  RE: Gapping between top of piinblock and underside of plate

    Posted 7 days ago
    Is the shape of the gap like a bubble? Typically, the plate screws can bend the plate a bit to correct for slight bends, but if it is just a short section that is warped (and I've seen those), they might not have sufficient force to pull the plate to the block - or you wouldn't want to bend the plate that much. I have had to do a little bit of epoxy fill on the backside of some plates to make for a flat surface to mate up to a pinblock. And yes, those were on Steinways.

    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 8.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 6 days ago
    I do try to fit that surface as closely as I can within reason. I have sometimes needed to remove wood "up the kazoo" both bass and treble due to the plate warpage, but just part of the job.

    I have considered Ed's idea of grinding the plate a bit flatter but have not actually done it. Maybe I will on the next one.  I will admit to having left a little gap here and there on some. No ill effects to point to.

    And considering some of the lousy fitting I've seen from the factory on some of these even at the flange (even though the block is entirely blackened as if it fit like a glove...), yikes!

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 9.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 6 days ago
    I like using hybrid blocks where I laminate an 8-10mm layer of Delignit to a multilam block. I had luck on a recent Chickering, which had a warped web area, by laminating the rough cut block and Delignit right on the warped webbing, using the warp as a form. It copied the warp pretty nicely, and had a little, but not much spring-back. I did not bother with too much top face fitting from there, as it was reasonable, and being a Chickering, not glued to the stretcher, which makes life easier..

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 10.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 6 days ago
    I appreciate responses, which have challenged some of my assumptions.  I'm travelling back from Boston (maybe I'll stop off next time Jim) so I'll respond then, but it raises a couple of interesting issues.
    Thanks
    David S

    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 11.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 6 days ago
    To keep this from getting out of hand (doubtful),  I'll try to summarize what's been said, either in consensus or in somewhat disagreement:
    - all seem to agree that Steinway plates are, to some degree, un-level in the area of the underside of the tuning pin webbing.
    - according to Jim I, Steinway strives to accomplish fitting as a specific stage of their process,
    - everyone (responding) makes some attempt to effect fitting of block surface to underside of plate
    - Jim I expresses reservation/doubt about the functionality of precise fitting of this aspect (certainly relative to flange fitting)
    - he references the design of open-face blocks by way of suggesting a vestigial (as per block stability and function)  of precise fitting
    Open face blocks have no restraining webbing on the top face. Those pianos can be stable. Bechstein's open face tends to rotate down in the front, but that's because the flange is not beveled.

    Discussion - dilemma
    - where then is the line (grey-area) between functional and non-functional?  If it doesn't make a difference, why spend any more than absolute minimum?
    - even allowing for the possibility that Jim is correct, one fundamental engineering difference is the resulting difference in the length of the exposed tuning pin... the distance from pinblock to string coil.  The difference in leverage on the pin and block seems significant.  All the more so, in this case, as the plate thickness seems remarkably substantial.  If I can, I'll measure.

    Ed McM seems to put more stock (and time) into this aspect by dressing underside of plate.  Jim asks how much material (i.e. thinning) Ed is comfortable removing. He says:
    All Steinway plates bow in the middle. This means one must remove the most material from the treble end. If this block has space there, they had to work to put it there.
    Since the term 'bow' could refer to either direction, I'm concluding from the full thought that the common presentation is a shape that's lower mid-span.  Is that correct?  If so, then my observation seems even more confusing, as I don't believe rebuilder would have 'gone to town' in removing block material. This might make more sense offending area were the last treble.

    I'd be curious to hear a bit more about Terry's epoxy treatment.

    Thanks.  It's always something.


    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 12.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 6 days ago
    There's another possibility....sorry David to add to your summation...

    The bow is generally in the middle of the plate. The gap you saw indicates an error somewhere other than the middle, as Ed said, which is odd. The gap should be in the mid section, not the treble. it may be that the top face fit was reasonable, out of the piano, but when they installed the plate via original Acoustic dowels and original height nose bolts, that the plate level, relative to their previous fit, was messed up.

    It is easy to do this, in a doweled installation. If you fit the top face out of the piano, but don't retain the relationship of the top face to the bottom face, when the block is glued in and on to the stretcher, ei the block bottom's original orientation to the stretcher and belly, the top face will be canted away from its original position. If you then retain the previous dowel and nose bolt heights, ignoring the fact that you canted the top face of the block when you glued it in, when the plate sits on the original height dowels and nose bolts, there will be a gap in the treble section, and the block screws will be stressing the plate webbing. I think this is a reasonable guess at what may have happened, given the treble location of the gap.

    The fix, is to re-position dowels and nose bolts to the new block conditions, after you put a new block in.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 13.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 6 days ago
    So far the most plate metal I have removed while flattening the plate is about 1.5mm at bass and treble. That usually reduces the curve enough to allow for a good enough fit. I start leveling in the bass area first and blend it to the middle region before I move up to the treble. Trying to use the 4' level as a flat gauge has limited precision. I do use a feeler gauge to advise me.

    If your face grinder is coarse enough, the material comes off surprisingly quick. Three hours maybe to make a great improvement. The way I work, this saves time over doing the wood alone.

    When I first thought of doing this I was worried the plate might continue to warp as I removed metal since piano castings are not stress relieved, but I can detect no movement.  Makes me think a foundry with CNC could grind/machine/drill a casting to the precision of plus or minus 0.5mm on all three axes. That would solve a lot of QC issues.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------



  • 14.  RE: Gapping between top of piinblock and underside of plate

    Posted 5 days ago
    David S. wrote: "I'd be curious to hear a bit more about Terry's epoxy treatment."

    The last S&S plate I wrestled with was generally bowed front to back rather than end to end. I roughed up the underside of the webbing to prep for epoxy application. Then I plugged the tuning pin and screw holes, trowled on epoxy while rough-leveling with a straight edge, let cure and then sanded flat using a straight edge as a guide. Redrilled plate holes. Picture show follows (sorry, pictures are likely not in logical order as I am having trouble organizing them as I post them):  The two photos that show a straight edge across the webbing and showing a gap were taken before applying epoxy!  ;-)


    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 15.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 4 days ago
    Good summary.

    Any small gaps in the web/block fitting is largely taken care of by the plate screws pulling the block snug up against the web.  It's not a bad idea, however, to make sure that the block can be pulled to the plate either by inserting some screws or testing with clamps.  If it's impeded from being pulled to the plate then the problem is likely the top edge of the block where it meets the flange.  Be sure to round that off.  I certainly don't want a big gap underneath the plate even if one can argue that it doesn't really impact stability.  There's really not much reason to leave a gap there except laziness.

    Fitting the block to the flange using a thick epoxy mix has been done for years and there are many mentions of it on the list somewhere.  Basically you use a 2 part marine epoxy (or similar) thicken it with some filler, spray the plate flange with a mold release (or rub car wax on there), lay a layer of epoxy mixture on the flange side of the pinblock, push it up against the flange, use clamps to insure that you squeeze out as much excess as possible and hold it in place while you drill and insert several plate screws along the web, cinch those down to pull the plate to the web and let the epoxy cure.  Before you remove the block drill the rest of the plate screws (since this is the final resting place of the block) mark where you will drill for the tuning pins with a centering punch and then remove the block.  Us a scraper to clean up any excess epoxy that has squeezed out (if you belt sand it smooth be sure to where a mask, epoxy dust is nasty stuff).

    Hint, before you lay on the epoxy, during the dry fit, mark a few tuning pin holes so you can be sure that you pull the block to the flange as close to the original position as possible.  That will insure that the fitting laying of epoxy is as minimal as possible.

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



  • 16.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 6 days ago
    Not much to add except that I do take time to fit the block to the underside of the plate.  The plate is always bowed some and so removing material from the top of the block is usually required.

    My method is to take measurements across the block in various places  along the length of the block measuring the thickness through the old tuning pin holes, at the front and back edges and writing those numbers on the top of the block to use as a guide.  Note that the stretcher side of the block often has a raised edge left from where the block was planed down so you have to account for that. Once I cut the block to size I then use a power plane to try and hit the thickness as close to the original as possible (assuming you want the same block dimension.  The differences in thickness are always a result of material removed from the top of the block.  After that I take a belt sander to smooth things over.

    Then, while fitting the flange it's easy to see if there is still a remaining gap and, if so, by rubbing the block against the bottom of the plate you can usually see marks where the high spots are and take those down accordingly.  Those areas are often along the flange, especially the tenor/bass break, and at both the treble and bass end.

    Any small remaining gap is usually remedied by the plate screws pulling the block up to the plate so I don't really worry about a perfect fit.  When glassing the block to the flange insert some plate screws and snug the block to the underside of the plate while the glassing material is hardening so that you don't get squeeze out from the flange fitting building up on the underside of the web and preventing the block from being pulled to the plate later.

    I would not be grinding cast iron if at all avoidable (and in this case it always is): it's hazardous (combustible) and toxic and can result in lung disease with repeated exposure (siderosis).

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



  • 17.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 5 days ago
    I do wear a dust mask and metal grindings are way less combustible than maple dust.

    ------------------------------
    Edward McMorrow
    Edmonds WA
    425-299-3431
    ------------------------------



  • 18.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 5 days ago
    I'm just looking out for you Ed ;-)

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



  • 19.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 4 days ago

    Grateful for responses.  It'll take a while to absorb. 

    A duality lingers:

    Jim seems to be the only one who goes out on a bit of a limb in suggesting that that fitting is of limited significance (at least the way I last read it).  While no one outright said that it's critical, your actions in trying to effectuate this interface seems to imply such... why else would you be trying so hard and resourcefully?

    Do you have some ideas as to possible ill effects?

     

    Again, thanks






  • 20.  RE: Gapping between top of piinblock and underside of plate

    Posted 5 days ago
      |   view attached
    David L. wrote: "When glassing the block to the flange insert some plate screws and snug the block to the underside of the plate while the glassing material is hardening so that you don't get squeeze out from the flange fitting building up on the underside of the web and preventing the block from being pulled to the plate later."

    Always glad to hear that someone else uses this technique to mate the block to the flange. I'm always impressed with the excellent fit I get. An alternative to using plate screws is to simple clamp securely.

    ------------------------------
    Terry Farrell
    Farrell Piano Service, Inc.
    Brandon, Florida
    terry@farrellpiano.com
    813-684-3505
    ------------------------------



  • 21.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 4 days ago
    David S.:

    IMO it is simply a matter of "the more physical contact with the plate, the better".  However, there comes a point where you need to say "enough".

    If SS had been able to produce perfectly flat and consistent plates throughout history I suspect they would have ignored the slight irregularities that might exist between the top of the PB and the plate webbing. However, since they were completely unable to do do (many wildly curved and uneven) they had to develop a means to deal with it, the "easiest" way being to rout the top of the block to conform to the plate (also obviously their 'inside out' method of construction would necessitate this).   Then, in true SS marketing MO they created the idea that if this were not done it would produce an unstable and inferior result.

    I have seen numerous pianos that it was obvious that the web was not fit, with visible gaps, and horrible plate bending (determined upon teardown).  Personally, in my early days of PB replacement I knew nothing about web fitting and did not do it (I concentrated on flange fitting). I specifically recall analyzing some of my early rebuilds after gaining knowledge of web fitting to see if there were any stability issues. I never found anything I could contribute to that. They were solid (even the ones done prior to using epoxy on the flange...solid [due to painstaking fitting]).

    So, I agree that it is probably functionally irrelevant. However, I don't like bending and twisting a plate to make it fit. Therefore I try to get a "pretty good" fit all the way around.  The last thing I want to see happen is for a plate to crack after I reblocked it, and then have it determined that I had not followed 'standard PB fitting protcol' but cut some corners. That's a lawsuit waiting to happen...and unnecessary IMO.

    Pwg

    ------------------------------
    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 22.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 4 days ago
    Just a point of clarification, I only use the epoxy mating method where the block meets the flange and I usually spend some time getting a pretty good fit before I do that.    I don't use it to fill the top of the block against the web.

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



  • 23.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 4 days ago
    David <While no one outright said that it's critical, your actions in trying to effectuate this interface seems to imply such... why else would you be trying so hard and resourcefully?

    While I don't think is absolutely functionally necessary to get a perfect webbing fit, or even a close to say 50% fit, I do it, because it makes fitting the flange easier. If the plate and the block, are warped in ways that don't allow the two to mate in a consistent way, when reading the chalk, it just makes the flange fitting and repeatable positioning, during fitting, plate screw location, and ultimately final plate height easier and repeatable. Its a real drag to fit carefully, then see things move when you screw it down. So a passive fit achieves this goal, separate from the functional (or not so functional) goal. So I go for a reasonable fit for this reason.

    That said, I really think, in this case, re your description, I'd wager that the fit was screwed up by the plate dowels and nosebolts, and not the block fitting.

    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 24.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 3 days ago
    Am I the David you are addressing in this post?  Doesn't seem so. But my comments anyway.

    How hard is it to mate the plate to the web and flange?  Not very. I do a pinblock fitting in about  an hour, often less.  Power plane and disk sander (I don't grind the plate). The final fitting (after the plate) is to adhere the block to the stretcher where you can apply the same principle as the flange with an epoxy mix. Drop the plate on top, screw the block to the plate and let the epoxy cure with everything assembled and screwed down. Dowel the ends to the inner rim
    and install a few angled dowels along the stretcher. Never had a block shift position after that.

    I'd like to think that a sense of craftsmanship sometimes trumps what is absolutely necessary functionally. Sometimes we take care to finish the parts that won't be seen as well as the ones that will. Nobody can tell, perhaps, but we can.

    (BTW Nossaman had a nice way of fitting to the flange which was to cut the proximal side of the block at a slight angle so you could then insert thin glued wedges between the stretcher and the block. When dry, trim flush and you're  done.)

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



  • 25.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 3 days ago
    An obvious reason for not having a gap between the block and webbing is pin height. Added flag-poling and inconsistent tuning 'feel'.

    ------------------------------
    Regards,

    Jon Page
    mailto:jonpage@pianocapecod.com
    http://www.pianocapecod.com
    ------------------------------



  • 26.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 3 days ago
    The other David...Mr Skolnik.


    ------------------------------
    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
    ------------------------------



  • 27.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 2 days ago
    I missed this post initially... computer problems.  Jon, if it were that obvious, somewhat less talented would have already mentioned it.  That was, in fact, one of my concerns, so thanks.

    ------------------------------
    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
    ------------------------------



  • 28.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 2 days ago

    Hello all,

    While perusing the various blog entries I thought that I might opine on this topic. I hope it is still timely and of some interest.  The original post referenced a Steinway piano, so all my remarks have to do with rebuilding Steinways. 

    The process of fitting the top of the pinblock to the bottom of the plate is something that should be taken very seriously as there is much more involved than meets the eye.  This is one of those points that we as rebuilders tend to overlook, or minimize the importance of,  that has irritated Steinway to the point of influencing their recent remarks and actions concerning rebuilders. This blog is not the place for a "how-to" on the subject but there are several basic principles we need to be aware of since much of what will happen in the future is based on fitting the top of the block to the plate web. Very briefly, and with most details left out, here goes:  The plate is suspended above the rim at a predetermined height with small spacer blocks representing the soundboard thickness, plate thickness and guesstimated acoustic dowel height which are laid on the inner rim.  When the block is shaped it is the first step of setting bearing, though we never think of it as such.  I specifically asked about the acoustic dowel height and was told that the goal is to have a relatively even bridge cap thickness from end to end when the down bearing is ultimately set. 

    Think of the position of the plate and compare it to an airplane that is about to land.  We set the pitch or string angle to rise 1-2 degrees as it moves toward the tail of the piano, like pulling the nose of the airplane upward.  The strings are intentionally not set parallel to the keybed.  At the same time the roll is set.  This is the bass to treble string height relative to each other. Yaw is the "crab angle" set into the wind which would be us trying to set the strike line parallel to the front of the piano by fitting the edge of the PB to the plate flange. This will be tweaked when the the stack is fit to the keyframe during fore finishing.  Also, the plate elevation (string height) is set. This is all achieved, less the flange fit, with  one cut on the top of the pinblock matching it to the plate.  I think this is an absolute genius way of building a piano - not that it is without its problems.  These "old timer" piano builders were not stupid. Having to shape the top of the block was not to cover up a mistake. Every plate is going to be warped a different amount and each block will be matched accordingly and not to a specific measurement.  This is the epitome of hand craftsmanship and the fact that the measurements vary is not evidence of laziness or inability.  One of the pics shows how much the PB was cut down in the factory to get all these parameters within tolerance. Also, bending the plate down to the acoustic dowels is intentionally done with the future bridge height/down bearing  in mind, just pay attention during tear down.  It is not the sign of a poorly designed piano. 

    When we have regulation problems that seem to be unsolvable, such as the problems of the CBS era, they can usually be traced back to quality control  in the plate positioning parameters. Many times the action can be made playable by custom bored hammers but this doesn't really solve the problem. If you're not aware of these parameters you can create some real headaches for yourself down the road.  Keep in mind that when the PB is shaped in the factory, the soundboard and bridges are not yet installed, so if you're installing a new block but keeping the original board and bridge without recapping you have a whole different set of obstacles to overcome to achieve proper down bearing by working backwards. 

    I have never seen a plate that didn't warp when it cooled.  I've heard that some other high end manufacturers will surface grind the plate web to be flat so it sits flat on the top of the block. I've heard that Steinway does this now but I don't know for sure. I think this is a great idea, never the less, that is not the world I live in.  I regularly find  0.150" of warp in the center of the web, measured bass to treble.  (see photo).  I don't see any way that grinding the plate will work in a rebuilding situation.  If not planned for in advance in the casting process the plate could be too thin and also there will be little control for final plate position (think of the orientation of the airplane). The pinblock will always be too thick when first glued to the rim and the cornice and it will be doweled in, right? Because you doweled it in, right? Of course you did.  So now, if you just lower the warped plate onto the flat top surface of the new block and tighten the screws you're going to be pulling the block up against the PB dowels. The PB laminations can be pulled apart by the screws.  So if you're going to pull the gap together with the screws then don't dowel the PB to the cornice. This is WRONG if you're rebuilding a Steinway.  On most other pianos it's probably won't matter.  FWIW- "Stretcher" is a furniture term such as a cross-brace  between chair/table etc., legs.  "Cornice" is an architectural term, e.g. capital, frieze, pediment, triglyph, etc.    BTW -  Steinway patented the "glass bedding" of the top of the block as well as the edge to the flange.

    After shaping the PB to the plate, the ends of the PB will be thinner than the middle by the amount of the warp.  Be aware of this if you are just going to restring the piano.  You might think you can get away with a longer tuning pin and then find them sticking out of the bottom of the PB in the bass or treble.  This is one of the downloaded pics where the tech's solution to his newly created problem was to grind off the ends of the tuning pins.  

    Included are some pics of the modified router I use to shape the block. I realize that they are of limited value as most techs will never build something like this but maybe some can glean a few ideas.  The frame is made from unistrut bought at Home Depot. The drop tube has a bearing in its end next to the chuck and is made from a worn out 30-06 rifle barrel.  This allows the cutter to be 8" below the surface of the router and not whip at high rpm.



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    Glen Hart
    Grand Junction CO
    970-434-5558
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  • 29.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 2 days ago
    I believe Shawn Hoar in CT built a similar arrangement, albeit somewhat simpler. He said he did it because people told him it couldn't be done. That's just the way he thinks. Wish I had one.

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 30.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 2 days ago
    Glen Hart hoped his post would be of "some interest". Nah.
    Before things moved on, I just wanted to thank him and everyone else for taking the question seriously and providing a wealth of information, which I haven't had time to fully digest, or read, for that matter. I'll have some time while Jim is off in Norway.  There's no internet in Norway, is there?

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    David Skolnik [RPT]
    Hastings-on-Hudson NY
    917-589-2625
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  • 31.  RE: Gapping between top of piinblock and underside of plate

    Member
    Posted 2 days ago
    There is no internet, and they get around in these real long oar powered vessels, and sing Viking songs.

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    Jim Ialeggio
    grandpianosolutions.com
    Shirley, MA
    978 425-9026
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  • 32.  RE: Gapping between top of piinblock and underside of plate

    Registered Piano Technician
    Posted 13 hours ago

    Warning:
    Sudden exposure to Glen Hart's sources and methods may result in a strong desire to set fire to your current rebuilding project. The one that ,until yesterday, you had felt pretty good about. Having proper safety equipment on hand is strongly recommended.


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    Karl Roeder
    Pompano Beach FL
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