Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Question re typical pinblock separation in a vertical

Hi,

I have a new client where the pinblock is separating from the core. There is nothing unusual about how this is occurring. It's the same pattern I'm sure we have all seen before.

The piano is also a bit more than 1/2-step low, so I shouldn't need to drop the tension to make the repair.

Normally, I would just drill, insert the bolts and glue, etc. one day. Then, return a day or two later, after the glue has had time to dry and cure, to pull the piano to pitch and fine tune.

But, this client lives a significant distance from me. To save her money, and save me time and gasoline, is there a way to reliably get all this accomplished in just one trip? Can all this be done in one trip and leave her with results as good as would normally take two trips?

Thanks,
-Joe

I have done it in 1 visit

probably 1 visit only. May be no need to make the tension lower than it is
is there any reinforcing part ?(I suppose the pinblock is open) ?
if possible a larger hole so the bolts does not protrude too much on the back if you cnnot find thick enough bolts with round head) (to avoid marks an the wall mostly)
the customer is certainly not exigent

A lot depends on how severe the separation is. Caught early enough, most are cosmetic and can be done without making a grand production out of it.

I have done 2-3 day servicing as an overnight house guest or staying at an hotel on expenses. Usually it is more formal if I am working on behalf of a company.

The only reason for an extra visit is the ts the tuning stability question and we have all done pitch raises that stayed put longer than they had any right to.

I would have no problem doIng the job and leaving subsequent tunings to a local tuner even when cost isn't an issue.

In the past, I have dropped the pitch very low to facilitate getting the gap closed tightly. Dropping the pitch by only 1/2 step from A 440 does not accomplish hardly anything regarding getting the pinblock back into original position. If you can do the repair with the piano at its present pitch, good for you. It sure makes things easier re: tuning stability afterward.

Thank you everyone for the replies. They are helpful
That's something that I really like about this forum... the brainstorming that's possible.

Isaac, The plate does extend all that way to the top.
The separation isn't excessive, but it is quite visible. It seems widest in the upper tenor/low treble area. Naturally, this is also the area that has gone the flattest.
This is a young couple starting out. So, they do need to conserve their resources.

I just wondered if anyone here has developed a strategy for making this repair, including pitch raise and fine tuning, in one trip... maybe by using C/A glue with yellow glue, or some other approach.

Maybe I'll stay with what I know. It seem that there is a good possibility that it could all be done in one trip, but that there are no guarantees as to tuning stability.

Thanks

If you use bolts that go right thru to the back of the piano, regular carpenter's glue sets in an hour. So I don't see how you could not do it. Extra clamps and wood blocks to keep from marring the plate would help as well.

Hi Jean,

I know it will set, but I think it takes about 12 hours or so to cure and reach its maximum strength. But, maybe most curing takes place earlier in the process with diminishing returns as the glue continues to cure?

Thanks,
-Joe

Yes, and the bolts will hold it.

I actually think in this case, since you won't be lowering the pitch more than it is now, it will actually allow you to pitch raise it 2 or 3 hours later. Just take that time to check regulation, vacuum, clean, go for lunch etc..

All the best.

That makes good sense. Make the repair, take a break. Maybe go to lunch and/or check out the local B&N or other stores, or Christmas shop, come back and tune after 3 hours or so.

Thank you, Jean.

-Joe

A pleasure, hope it goes well.

Tape off each side of the open joint. Mix up some slow setting (and thin) epoxy and, using a syringe, lay a bead along the length of the open joint. Using a thin metal strip -- I use a long, very thin fillet knife -- work as much epoxy into the open joint as you can, refilling as you go. When you have filled the opening completely tighten the screws/bolts/whatever and pull the piano to pitch.

Slow setting epoxy will keep seeping into the open joint for some time so it may be necessary to keep filling it up for a time. It will go places ordinary glue never thought of going. Eventually it will fill up. Clean everything up, fine tune the thing and go home.

ddf

If gaps are left, epoxy is the way to go, for sure. In a customer's home far away, it involves a lot of preparation.

If you think that with new bolts counter sunk right through to the back of the piano will work, do a dry fit first, just see if the bolts can actually pull the assembly back together, then use carpenter's glue and just squeeze the thing.

If not, epoxy for sure.

If the piano still has good sound, as is, just fill it with epoxy, like Del said. Just prevent it to go further.

How wide is the separation, 1 mm or 2?

Joe,

I know that time is of the essence in this case. Nevertheless, I wanted to ask whether you'd be prepared to make a few snapshots of the defect (before, during, after repair) and post them afterwards - perhaps in some album to which you can provide the link here.

I've been searching for pictures on pinblock separation (and its repair) for sometime, and though I've found a few, I'd like to learn more about
* where the separation typically takes place, and how to look for it (especially if there's a board or veneer covering the top of the pinblock)
* how large it can sometimes be
* how to repair it, etc.

If, however, you're too busy to take pictures, I understand completely. I just thought I'd ask.

I belive all depends of the type of separation but I would no try to use slow epoxy if it is thin ( I guess it is most of the time) I would be afraid to have to pour half a liter and to have some coming frol below the plate on the soundboard

The bolts are doing most of the job, to me. If they cannot the repair is difficult.

That sort of thing proove how much a plate can bend without breaking..

And that is one of the problems with this kind of repair. How long has the separation been there?

This is why I always use clamps to pull the parts together previous to applying any adhesives. If the separation goes together without breaking the plate then I slacken off the clamps and complete the repair.

Pony clamps on a black pipe usually do the trick. Or large gauge C clamps

Hi Mark and Jean,

If the customer allows, I will take a few pics when I'm there. As they say, a picture is worth a thousand words

Del, I do understand about the advantages of epoxy. But, this will then take two trips, I guess.

I was considering using fresh liquid hide glue. I know hide glue has good gap filling qualities from the player training I've had. The bottled hide glue is just hide glue with urea added to slow drying.

One way I do vary from most folks when making this repair is that I do not like to use carriage bolts. They can rotate in the wood when tightening the nut. Hex head bolts are very controllable from both the head side and the bolt side with a socket set and a wrench. Add a few appropriate washers and a heavy leather gasket on each side. This has always been a very safe approach for me. I have never had a plate crack.

Another way I vary is that I sometimes place the nut on the back. It's easier to cut the excess off the bolt that way, minimizing the risk of any damage to the plate or pins. Then, file things down a bit so there are no sharp edges.

When the glue is dry, if you really want to make things like original, you could remove a bolt at a time, install a hardwood dowel, re-drill, and the reuse the original screws or lag screws.

Mark, one thing to be careful of is the location of the hinges for the lid. You don't want to install bolts and then not be able to re-install the lid hinges.

I've never used liquid hide glue for this job, but have for other jobs. Sounds good to me.

Hi Mark,

The customer consented to having some pics taken and posted online. I'm not much of a photographer, but I gave it a shot.

The pinblock/core/backposts glue joints were originally obscured by green felt. Even though the backposts obviously moved, I assumed that there would also be a separation between the pinblock and the core. After removing some of thwe felt, once I was given the OK to proceed, a different story emerged. Several backposts moved out of position, but the block/core glue joints remained solid. Notice the wavy back.



Below are two more pics of the backposts separating:




Below is a pic of the back after the plate screws were removed (remove one screw, drill, insert bolt, snug up enough to make contact, go to next plate screw...). You will notice that I used several washers, getting wider to trry to distribute the force over a wider area,, including lock washers. i also decided to go with a cork washer made from cork suitable for player gasket work, rather than leather. The plate was very smooth, so i decided to use cork. The reason I use soft washers to contact the plate and the back is that just in case there is some irregularity, the hope is that the soft washer will compress more, rather than applying an extreme amount of force to just one area. The cork washer will later be trimmed when I return to finish the job.



The plate screw hole would have been too far off center from the backpost to have been of any value trying to force it back to its original position. So, I drilled directly through the plate to install a bolt there. I really don't like doing this because there is risk, but in this particular case the risk seemed worth the potential benefit.



Taped off and ready for gluing



Pole clamp to try to pull this separation back. In this case, the screw hole was also off center somewhat from the backpost. Unfortunately, the tuning pins would have interfered with drilling a new hole and the insertion of a bolt in a more ideal location. So, I opted to install a bolt near the backpost, and use a pole clamp overnight to try to pull the gap closed as much as possible.


Since I was working with a slow drying glue, I didn't need to rush to try to close the gaps. These gaps were stubborn. Not wanting to break the plate, I finessed, a little at a time, closing the gaps. I tightened a little, then walked away. Tightened a little, walked away, etc. But after a while, no more glue would come out when I tightened and the gaps would close no further. The only thing that would happen is that the washers would start sinking further into the back.

The job doesn't have to be perfect, just stable. Some of the gaps are not closed completely and one gap was just too stubborn to make a whole lot of progress. I didn't want to force things and risk damaging the plate, so I stopped when it seemed that there could be no further progress. Between the glued and the bolts, the piano should be stable. I will return on Thursday to finish the job and then tune the piano. The tuning will tell me about the success of the repair.

Many thanks, Joe, this was interesting to read.

In all the uprights I've looked at thus far, the top of pinblock/core/back area was covered by some board (often serving as the rear half of a split lid), and in many cases the top part of the back and posts was also covered by some thin board. This has always made me wonder how one can assess a used piano for pinblock separation. It appears to me that one really can't... (other than catastrophic tuning failure or instability.)