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Epoxy and Repin Bridges

  • 1.  Epoxy and Repin Bridges

    Posted 30 days ago
    I have an old upright that I am using to practice some repairs that I have not yet done for clients and to practice skills towards the RPT exams. My Salt Lake PTG chapter meetings are a 2.5 hour drive away for me, but they have started doing live streaming of the meetings so I am able to participate. I have also attended a repair workshop for our chapter and am finding these things exciting and rewarding to learn and practice. I find myself also learning so much from these discussion threads. I was unfortunately unable to attend the Tuscon Conference this year, but am planning to attend the convention next year.

    I am doing my first attempt at epoxying and repinning the long bridge on my old upright which has developed the occasional hairline cracking.

    I have several questions for some of you experts. All of the pins from the long bridge are measuring at .086. The new pins I ordered from Schaff are supposed to be .086, but seem to be measuring about .002 or so smaller than that. At any rate, they do not fit quite as snugly as the original pins, which are bent and with some corrosion. I am planning to lightly sand out string grooves and re-notch to bisect pin hols for clean string termination on the bridge, fill the holes with epoxy, let cure, and redrill before pinning. Should I be concerned at all about the slightly loose fit of the pins here? Is it better to apply epoxy and then insert the pins?

    While I am at it I am also wanting to work on the bass bridge. It is in good shape with no cracking, except for a few hairline cracks from sidebearing pressure. I was planning to epoxy and repin as well. However, the monochord pins measure at .140. Again, the question is, can these be filled with epoxy and redrilled for new .135 pins, or is it best to plug with maple dowels and redrill? I also considered using a .146 desk pin, but wouldn't want to change termination for the strings; is this an absurd idea, or worth considering? Any other ideas for handling non-standard bridge pins? Really, the point of all of this is for me to practice, so I have also considered having the bass bridge duplicated or  for me to practice recapping for more standard pins.

    Again, my main goal here is to practice correct procedures, and build muscle memory from the hands on experience. Any advice would be helpful for me in the learning process. Thank you!

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    Alden Jack
    Smithfield UT
    435-760-3974
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  • 2.  RE: Epoxy and Repin Bridges

    Posted 30 days ago
    If it is not already sitting in front of you, Bill Spurlock's detailed description is in the August 2015 Journal.

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    Floyd Gadd
    Regina SK
    306-502-9103
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  • 3.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    Thank you for the suggestion. I have read Reblitz and the Pianos Inside Out texts, but hadn't read this one yet. I read through it and found it helpful and consistent with the others. Spurlock also made note that the new pins from supply houses are sometimes  .002 smaller than the new ones and recommended redrilling for one size larger pin in this case. I am wishing the long bridge didn't already have 7 size .086 pins. It seems like size 8 is way too big for the long bridge. 

    The article also does a great job walking me through sanding, retouching, and gluing. This is one I'll print and out in my shop reference book!





  • 4.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    Alden,

    Have you already removed all the bridge pins?

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 5.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    I have removed two from each section to measure with a micrometer, but I have not removed any others.





  • 6.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    Pianotek has plated pins which are a few thou over the originals.

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    Regards,

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



  • 7.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    Thank you Jon on the tip about pins from Pianotek. Are they noted differently in sizing, or do they carry standard name sizes, but simply measure slightly larger on the micrometer?





  • 8.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    I have a technique I have developed regarding repining an existing bridge you might want to consider. It is only useful on bridges with "healthy" wood. (Soft, punky wood will give soft punky tone. There really is no substitute for fitting new bridge caps in that case). I have done this procedure with the slightly undersize new bridge pins to "solve" the fit issue.

    After removing the old pins and brushing away the dust with a dry tooth brush, use a small syringe to put some water into the bridge pin holes. Let dry overnight. Then re-notch as needed. Next run just enough water thin superglue into the bridge pin hole topcoat the inside of the hole. You must be very careful to only apply that amount or you will have to drill the holes again. Install the new 1" bridge pins, (copper plated mild steel, not nickel plated or stainless steel. If the holes are not deep enough for 1" pins, drill them and be sure to drill properly undersize. I have my well experienced reasons why I only use the copper plated pins but that is another too long story to tell here.). Use a nail set to drive the pins to final height. Then apply thin superglue around the bridge pins and over the surface of the notch. Let dry overnight and file pins to level them out.

    While you are doing this you may also find it helpful to shape the V-bar to a true V-shape.

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    Edward McMorrow
    Edmonds WA
    425-299-3431
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  • 9.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    What if you don't want to repin?
    I have a 1990s Baldwin upright that the pins seem to have been pushed out of the hole by the climate changes. Hydraulic I think it's called.
    I was going to wick CA glue around the pin. Doesn't that act as the glue sizer like when you do the tuning pin treatment? And then drive them back in so they are all at the same height and instant cure.

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    Keith Roberts
    owner
    Hathaway Pines CA
    209-728-2163
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  • 10.  RE: Epoxy and Repin Bridges

    Posted 29 days ago
    Oh,, you wouldn't fill the holes with epoxy and re-drill. The difference in the hardness will cause the bit to wander into the softer material. You will never get the hole to center where it was originally.

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    Keith Roberts
    owner
    Hathaway Pines CA
    209-728-2163
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  • 11.  RE: Epoxy and Repin Bridges

    Posted 28 days ago
    Ed,

    Are you using the water to ever so slightly swell the inside of the holes as well as a grain raiser? Or is there some other significance to the "water/primer" treatment that I'm missing?

    Alden,

    Why not just turn the pins upside down and drive them back in? Then treat each pin with a few drops of CA at that point?


    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 12.  RE: Epoxy and Repin Bridges

    Posted 27 days ago
    Peter, yes the water swells up the wood and the CA sizing "locks" it in place. Then after the new slightly smaller diameter pins are installed they fit tight and can be CA "welded" to the bridge. I have done a couple of Samick grands where I replace the nickel plated bridge pins with the 1" copper plated. The original pins are quite short in the treble but the holes were all drilled at the factory to fit 1" pins. Go figure!

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    Edward McMorrow
    Edmonds WA
    425-299-3431
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  • 13.  RE: Epoxy and Repin Bridges

    Posted 26 days ago
    Thanks Ed,

    I have one in the shop right now that may need this treatment. Willing to give it a go.

    Pwg

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    Peter Grey
    Stratham NH
    603-686-2395
    pianodoctor57@gmail.com
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  • 14.  RE: Epoxy and Repin Bridges

    Posted 25 days ago
    Thank you Ed for the description. I appreciate it!

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    Alden Jack
    Smithfield UT
    435-760-3974
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  • 15.  RE: Epoxy and Repin Bridges

    Posted 25 days ago
    Thanks for the suggestion on turning pins upside down Peter. That will probably been the only thing I can do for those .140 pins.

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    Alden Jack
    Smithfield UT
    435-760-3974
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