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Piano Key Noise
#2898086 10/08/19 01:25 AM
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I am almost certain that the pianokey noise I need to eliminate is caused by worn holes in the bottom of the keys that fit over the center rail pins. The noise is fairly subtle but annoying none the less. Pushing the key back and forth suggests that there is a little more play than there should be. They keys have been rebushed competently, the looseness is only in the bottom of the key.

When the key returns to the rest position there is a slight scraping sound. The sound is not coming from the action and I am almost certain it is from the center rail pin hitting/scraping the hole in the key. If I gently press the key back while it is returning the noise disappears.

I am considering various ways to fit the keys tighter to the center pins. I have not found any tools or repair parts to do this.

I am considering a sleeve on the center pin of either relatively hard plastic such as a thinwall teflon tube. I would have to ream or mill the hole in the key oversized to accommodate this sleeve. The sleeve could also be thin stainless steel tube. The problem I anticipate with this is that the sleeve might drift out of position.

Another possibility is a bushing inserted into each key. This could be a flanged bushing or a straight one. Straight would be easier to make but there might not be enough wood to hold it. I have a CNC router that I can use to make the recess for any type of bushing that I can make. I can also mill a slot across the key and insert a new piece of wood with a precisely drilled new hole.

I could use oversized pins but can not find any.

Are any of these ideas reasonable or are there any other solutions?


Spencer Chase
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Re: Piano Key Noise
spencoid #2898088 10/08/19 01:41 AM
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I glue in some paper to shim the hole to the proper size. I stick it in, making sure it does not extend too far, and stick a key pin in to hold it and mold it. Works fine!

Paper is nothing but shredded wood glued together, so it is just like what was there, except a little more dense.


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Re: Piano Key Noise
spencoid #2898091 10/08/19 01:57 AM
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good suggestion. i would guess that the hole is worn out of round. the paper would shim all sides of the hole equally. is it necessary or advisable to ream the hole evenly round before gluing in the paper? or does the pin make it uniform? what glue do you recommend? suggested type of paper? thin? dense? hard or soft?


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Re: Piano Key Noise
spencoid #2898095 10/08/19 02:11 AM
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I only shim where it is necessary. If it is loose in all directions, I will make a tube first, and shim that as necessary. But otherwise, if it is oblong, I will line up the key with the rest to figure out where paper should go. The pin will do the final placement and shaping.

The paper depends on how misshapen the hole is. Usually there is a lot of space to fill, so I use what I use for my business cards. Wood glue (Titebond) is fine.


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Re: Piano Key Noise
spencoid #2898098 10/08/19 02:58 AM
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I have not examined a lot of keys in detail but i think that most are worn. they keys were recovered and rebushed previously and this seems to have been done well but nothing was done to the holes.

Does it make sense to ream all the hole uniformly and to then be able to use the same amount of shimming? I have the ability to make all sorts of tools. I have a very accurate CNC router that I can make a fixture for that will allow me to make very hole exactly the same amount of oversize. I have very small carbide router bits that I use for making small holes.

I was considering making or finding bushings but doing this without changing the height of the key seemed like a problem. For that reason I really like the ides of paper for shimming.

I could also glue in wooden plugs and then cut a new hole with the router. Most wooden dowels I can find would be too soft but maybe bamboo skewers would make good plugs. Trying to determine the best way to fix all of the holes most precisely with the least amount of work.

I am away from the piano (or any other one that I can take apart) for about a month and am trying to use spare time I have to figure out a plan. I do not know how deep the hole in the key bottom is before it opens up to a wider space. Obviously the depth of the hole is not that great or the key could not tilt. If the depth is great enough I could make bushings of a long lasting material such as nylon or a reinforced fluroelastomer that could be simply inserted into carefully cut holes but there would need to be either a bottom to these hole to hold the bushings from rising up or they would need to have a flange and a stepped hole made. I can program the router to make any pocket that I want but I don't want to make things any more complicated than necessary.


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Re: Piano Key Noise
spencoid #2898128 10/08/19 06:49 AM
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I have had very good results from simply glue-sizing the balance holes, even when the wear was pretty extreme. I've used both hot hide and water-based yellow and white glues for this. Thin the glue to a water consistency. I take a balance hole-sized artist brush and paint the hole with very hot water then immediately follow with the glue. The point is to first swell the hole and then seal it with the thinned glue. You can do this without wetting or damaging the new bushings. After drying overnight you'll need to ease the hole(s) as usual with the tapered burnishing tool. I like to first coat the hole with teflon powder, which gets burnished into the hole as its eased.


Mark Dierauf, RPT
NH Pianos
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Re: Piano Key Noise
spencoid #2898135 10/08/19 07:16 AM
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Would the same technique work with CA glue?

Re: Piano Key Noise
spencoid #2898170 10/08/19 08:59 AM
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Greetings,

Don't start drilling out you balance rail holes! There is a permanent, easy, repair. It involves making a cut the thickness of a back-saw's kerf across the bottom of the key so the the cut is located across the worn side of the balance rail hole. It needs to be 3-4 mm deep. Into this slot you glue a piece of veneer. When dry, trim the veneer flush with three sides of the key and then use a small rat-tail file to make the hole round again by grinding out some veneer. It takes less than a minute per key, once you have all the stuff laid out.
I know, I know, this is old school, but I have watched keys so repaired maintain key tightness for 30 years at a university. If you want to repair your piano, do it right!
Regards,

An additional edit: I question why someone would rebush keys and not address pully keys. Given that, if you have the keys off, check the thickness of the sole plates, (the part of the key in which the balance rail hole is drilled). They should not be thicker than 4 mm. If so, get the tool to fix that before you worry about other things.

Last edited by Ed Foote; 10/08/19 09:03 AM.
Re: Piano Key Noise
spencoid #2898187 10/08/19 10:33 AM
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I like the kerf and veneer idea. I think the looseness is along the long axis of the key because the key return noise is quieted if I press the key back a little. This would make it difficult to use a back saw to make the kerf but I could either make two cuts at a sharp angle. I could also program the router to cut a 3 mm kerf along the key long axis down the middle. I need to examine some keys and see where the looseness is. First I will see if just sizing the holes is enough as that is surely the quickest repair. Then figure out what is the next step if that doesn't work. I'm glad I asked on this forum before doing something complicated like making bushings.

About the additional question: I got what I think is a good deal on the piano. Someone put a lot of effort into it about 30 years ago and then it sat. What they did, they seem to have done well but other things were not done at all. Recovering of the keys and doing the bushings was done well but the sloppy holes were left. They did a good job or restringing but did absolutely horrible action regulation or maybe none at all. They did a decent job of rehammering but never finished that either. They replaced damper felt quite competently but never regulated the dampers. My theory is that someone started the piano and either died or lost interest. Anyway,$3000 for a 9 ft Knabe refinished with new strings pinblock, soundboard work and hammers seemed like a good deal. It already is a pretty good piano but I want it to be a great piano.


Spencer Chase
Re: Piano Key Noise
David Boyce #2898475 10/09/19 06:09 AM
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Originally Posted by David Boyce
Would the same technique work with CA glue?


I don't think that you'd want anything that dried too hard. Any hardness would tend towards noisiness although I've never had them loosen up after sizing


Mark Dierauf, RPT
NH Pianos
Piano technician & rebuilder since 1978
www.nhpianos.com
Re: Piano Key Noise
spencoid #2898632 10/09/19 01:33 PM
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would tightbond (whatever the best one is)be too hard? i will try sizing first and then if this does not work will probably cut a shallow pocket into which a chunk of veneer with a half hole in it can be glued. this will allow making the hole a very close fit.hopefully the sizing will fit as cutting out the veneer pieces and the pockets will be a big job but fun. might be an excuse to finally get a cutting laser head for my router.


Spencer Chase
Re: Piano Key Noise
spencoid #2898647 10/09/19 02:23 PM
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I've been using Elmer's Glue-All for years to size and minimize noise, following a suggestion I saw on the PTG technicians forum. I believe the person posting commented that because of the softness of the glue, balance hole sizing is the only thing this product should be used for in piano work.


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Re: Piano Key Noise
spencoid #2898708 10/09/19 05:42 PM
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If you steam the bottom of the key at the balance rail with a wet sock and an iron for a minute, you will probably find that the holes swell up enough to fit the pin tightly. After the steaming, you can glue-size the hole with 50% diluted tite-bond glue using a toothpick to spread it around the inside of the hole at the key bottom. This will probably make them tight enough you may need to ease the hole slightly with a balance rail pin hole easing tool.

This glue sizing process is standard in good piano shops and factories.


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Re: Piano Key Noise
spencoid #2898806 10/10/19 02:19 AM
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Thanks Ed. this sounds like the best thing to try first. I doubt there is enough enlargement to warrant any of the very complicated things I thought about doing.There is probably just a little slop. It doesn't take much to make an annoying noise when the noise is inside an acoustic amplifier. I no longer live in Edmonds or the simple solution would be to have you fix it smile I am away from the piano for a month so I can only entertain ideas, not implement them which is probably good as I have had the chance to get suggestions from this forum before I had a chance to screw things up.


Spencer Chase
Re: Piano Key Noise
spencoid #2898861 10/10/19 08:05 AM
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Correcting the BR hole should also have the collateral effect of improving your sense of control over the key, and clarity of tone. Good snug fit makes a better foundation for everything else.

Pwg


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Re: Piano Key Noise
spencoid #2899439 10/12/19 08:09 AM
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On one piano, after sizing the BR hole with a water/alcohol mixture and, of course, allowing it to dry, I applied a few drops of wicking-grade cyanoacrylate to the hole. That really strengthened and hardened the wood. I doubt those BR holes will ever need attention again. I've wondered more than once why piano keyboard manufacturers don't harden the wood at the BR hole with some material or another. It would seem like a cheap and easy way of improving their product.

Re: Piano Key Noise
spencoid #2899460 10/12/19 10:51 AM
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I did experiment with thin CA for BR key-holes, I found that it made the keys noisier and I just don't feel confident about how well it will work over time. One can reverse CA to some degree by cleaning with acetone. But I felt it would block the wood from accepting any later steam treatment/glue sizing option as well.

Have you been able to observe the piano over time you CA the BR holes in? I would like something like that treatment to be useful.


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Re: Piano Key Noise
spencoid #2899517 10/12/19 01:31 PM
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I've had problems with CA making noise as well. When they are loose I always steam them first which takes care of 90% of the keys. Any remaining loose keys get glue sized. If the key is actually damaged, I route a slot on the bottom of the key and glue in a new balance hole insert.


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Re: Piano Key Noise
Ed McMorrow, RPT #2900115 10/14/19 12:28 PM
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Originally Posted by Ed McMorrow, RPT
I did experiment with thin CA for BR key-holes, I found that it made the keys noisier and I just don't feel confident about how well it will work over time. One can reverse CA to some degree by cleaning with acetone. But I felt it would block the wood from accepting any later steam treatment/glue sizing option as well.

Have you been able to observe the piano over time you CA the BR holes in? I would like something like that treatment to be useful.


I didn't have the piano for long, but the keys were quiet. Later resizing, if required, could be done by putting a thin coat of CA over the existing CA. However, considering how soft the wood is that some key makers used, and considering that those BR holes often lasted for years, I would guess that the CA-hardened wood would last much longer.


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