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broken key repair

  • 1.  broken key repair

    Posted 07-08-2022 16:57
    Been a long time since I've done one of these.  Is splinting necessary?  Very tight key spacing.  Bad break with very thin wood to work with.
    Carpenter's wood glue still the way to go?  Concerned about it getting into the balance hole.  No key buttons on this (Samick) key.

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    Timothy Edwards
    Beckley WV
    (740) 517-7636
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  • 2.  RE: broken key repair

    Registered Piano Technician
    Posted 07-08-2022 17:03
    Tim

    Yes, you can use carpenter's glue.  I presume this is right at the balance rail hole. To strengthen the key, I would recommend a splint of some sort. If you have veneer, finem but in a pinch I've used a business card 

    WIm





  • 3.  RE: broken key repair

    Member
    Posted 07-08-2022 17:04
    Use the adjacent keys as splints to align the dog-leg and level. Place waxed paper between the keys. PVA glue OK. Reinforce the break with thin veneer, with the grain horizontally, or fiberglass. Keep the balance hole free to remove any glue with a thin dowel or pipe cleaner.
    Glue on reinforcement after the keystick has been glued between the splints.

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    Regards,

    Jon Page
    mailto:jonpage@comcast.net
    http://www.pianocapecod.com
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  • 4.  RE: broken key repair

    Registered Piano Technician
    Posted 07-08-2022 19:05
    I'm not sure if this adds strength, but on the last one I had with scant clearance I applied stiff brown grocery bag paper and saturated it with ca. Then I sanded it a bit. It's held up so far but the break provided a lot of surface for the glue joint anyway so the splint might not have been too relevant.

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    Steven Rosenthal RPT
    Honolulu HI
    (808) 521-7129
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  • 5.  RE: broken key repair

    Posted 22 days ago
    Hi Jon,
    Had to use the fiberglass.  Not enough "spare" wood on the key for sanding to apply veneer, and insufficient clearance to apply veneer without sanding.
    I had forgotten about the wax paper "trick".  Thanks.

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    Timothy Edwards
    Beckley WV
    (740) 517-7636
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  • 6.  RE: broken key repair

    Registered Piano Technician
    Posted 07-08-2022 19:07
    I would use Titebond II for the initial repair. Insert a dummy balance pin to keep the balance hole clear. After wood glue is dry and you're satisfied with the repair, i.e., correct angles etc., "paint" epoxy resin on each side of the key. For added strength, apply fiberglass cloth to the side of the key. The repair will be stronger than the original. Unfortunately, this is not a field repair.
    Roger

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    Roger Gable RPT
    Gable Piano
    Everett WA
    (425) 252-5000
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  • 7.  RE: broken key repair

    Posted 07-09-2022 09:40
    As others have suggested, initial glue up with wood glue followed by splinting with thin (maple) veneer is the way to go. I consider this to be a "in-shop-job" as I like to let the two glue-ups each sit clamped overnight. If, as in your case the spacing is tight, sand down the splint area before the the splint is glued and clamped to allow sufficient clearance. I believe that since the original broken or fractured key was weak, sanding it is better than sanding the veneer after the splint is glued. Also, make sure the grain of the splint runs horizontal. I recently came across a fractured previously splinted key that failed because the splint was glued with the grain oriented vertically. For that one, I glued and clamped it on site and re-installed it at the end of the tuning...we'll see if that was good enough?    
    Gary Messling







  • 8.  RE: broken key repair

    Posted 07-09-2022 10:45
    If the key spacing is tight, you could perhaps sand the adjacent keys ever so slightly as well?
    I've done this on a few occasions and found no problem afterwards.
    Peter


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    Petrus Janssen
    Peachtree City GA
    (678) 416-8055
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  • 9.  RE: broken key repair

    Posted 22 days ago
    Hi Roger,
    That fiberglass/epoxy splint worked great!  Thanks for the tip!  Wasn't enough wood on the key for sanding, and not enough clearance between keys to apply a veneer splint without sanding.  The fiberglass/epoxy added almost NO width to the key after clamping.

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    Timothy Edwards
    Beckley WV
    (740) 517-7636
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  • 10.  RE: broken key repair

    Registered Piano Technician
    Posted 18 days ago
    Timothy,

    Thank you for airing your success story. About 25 years ago I was working on a 60's Steinway 'D' that had a noticeable flex in the long key sticks. The flex was so great, it felt as if the hammers were checking on the upswing – slow acceleration. I stumbled upon the idea when I smelled epoxy being used on an unrelated project by my assistant. I simply applied the epoxy on the side of all the keysticks. It worked. Since then, whenever I encounter a flexing keystick I find the epoxy is quick and effective.



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    Roger Gable RPT
    Gable Piano
    Everett WA
    (425) 252-5000
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  • 11.  RE: broken key repair

    Registered Piano Technician
    Posted 21 days ago
    Over the years I have used Titebond to reglue broken keys but I often reinforced with a material known as "fish paper", which is a very tough fiber paper used to insulate transformer cores.  Past sources of this were permeable enough to bond well with Titebond and it is thin enough not to interfere with other keys.

    Recent supplies of fishpaper tend to be less permeable and don't bond as well.  Kraft paper (grocery bags) is not as tough.  There is a Japanese fiber paper known as kozo paper that might be as strong and would certainly take glue well, but I haven't yet experimented with it.

    I found a French cotton thread at a store that I was unable to break without cutting my hand; almost as strong as dacron.  It would seem that long fiber paper made from strong cotton could be as tough as any other.

    It might be worthwhile to investigate kozo paper for key reinforcements.

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    Blaine Hebert RPT
    Duarte CA
    (626) 795-5170
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