Bridge lifting repair

Discussion in 'Acoustic Heaven' started by ghostchord, Oct 25, 2021.

  1. ghostchord

    ghostchord Tele-Holic

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    This is a guitar I posted here a while back about fixing a crack in the heel. The fix is holding but as I was playing it today I noticed another issue, not sure if it's new or just that I didn't notice it before:
    upload_2021-10-24_22-12-49.png

    As you can hopefully see one corner of the bridge is lifting. Should I just get some glue in there and try to clamp it down somehow? (I think I used screws through the pin holes in the past) or does the entire bridge need to come off? I think it's lifted high enough that I can get some decent amount of glue in there. Which kind of glue? I'd assume generally PVA is good for this job but CA will probably wick better in there? Water diluted PVA?

    EDIT: Took tension off the strings and it's not coming back down.

    EDIT: Doing a bit of research it seems a common cause is the finish getting under the bridge in which case the bridge apparently should be removed, the finish underneath it removed, and the bridge reglued. What do folks here think?
     
    Last edited: Oct 25, 2021
  2. lil scotty

    lil scotty Tele-Holic

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    It could be a symptom of your flattop not being flat anymore. That is a larger issue that should be investigated with a straightedge.
     
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  3. Peegoo

    Peegoo Doctor of Teleocity

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    A proper repair for a lifting bridge is to remove it and then scrape all glue from the top and the bridge. Inspect the internal bridge plate for damage and make any necessary repairs there.

    Re-glue the bridge to the top, using clamps.

    If you have no long clamps, you can use two 6-32 machine screws through the two E string bridge pin holes, with large padded washers and nuts on the screws to compress the bridge to the top.
     
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  4. Killing Floor

    Killing Floor Poster Extraordinaire Silver Supporter

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    I had an acoustic guitar bridge pull up. I took the to a pro because I’d mess it up. Cost about $70 and it’s good as ever.
     
  5. Boreas

    Boreas Poster Extraordinaire

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    I would definitely remove it. The two adjustment screws are a concern. What are they attached to? Do they go through the top and attach to the bridge plate? If so, the lifting bridge could split the plate or the top. It looks like the bass side adjuster could be detached. I would get it checked out ASAP to minimize potential damage.
     
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  6. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Do not just "get some glue in there and try to clamp it down...." for several reasons. First, new glue doesn't stick well to old glue, you need to get the old glue off. Second, if there is damage to the top like splintering or loose fibers you need to clean that up. If there is any old finish on the top, ditto.

    The bridge to top joint is the most highly stressed glue joint on an acoustic guitar and failure is common. Frequently a little heat ("I only left it in the car while I went in to get a latte") was involved.

    As has already been said, the proper fix is to remove it completely (heating blanket and a pallet knife), clean every bit of old glue off both the top and the bridge, sand the bridge to fit the curve of the top. The correct glues are either AR (Titebond original) or hot hide (which you won't be set up to use so there is only one choice). Clamp the bridge, including the wings, tightly to the top during the repair. There is a very good chance that glue will squeeze into the pin holes and glue whatever you've used for a caul to the inside - cover it in waxed paper). Once the glue has cured drill out the pin holes and ream them - they will be full of glue.

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    Unfortunately you are correct that one of the big causes is that finish is not completely removed where the bridge foot print will be. Fender acoustics seem to be particularly bad about this. The only fix is to remove the bridge and remove the finish so you have wood to wood gluing surface.

    As far as the adjustable saddle thing - that was popular during the 60's and 70's but many people don't like them. Once you get the bridge glue back on you can decide what to do (its a separate issue). Choices are to live with it and use it or to convert the guitar to a standard saddle in a slot, which does take some special tools.
     
  7. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I can put you in contact with someone in Vancouver who can do these repairs.
     
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  8. JL_LI

    JL_LI Poster Extraordinaire

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    This isn’t funny and is a little off topic but it brings to mind the time when the draw bridge in Woods Hole, MA got stuck in the open position cutting the town in half.
     
  9. ghostchord

    ghostchord Tele-Holic

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    Thanks... This guitar is not worth paying someone else to do this and at any rate I'd probably do it myself unless this was a very expensive instrument. I've already replaced a bridge on one acoustic successfully... though in that case the guitar I repaired had the bridge pretty much completely off and broken and I installed a new bridge to replace it, this would be the first time I try to use heat to get a mostly installed bridged off. I think I can handle the rest of it. Would need to find my old clamp or make a new one or something.
     
  10. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Here is the little silicon heating blanket that I use, a few minutes with this on and most bridges pop right off

    0607201404.jpg

    I very lightly clamp in on and just keep working the pallet knife around the edges.

    The important thing is to get every bit of old glue cleaned up and if there is finish under there to get it all off to bare wood.
     
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  11. ghostchord

    ghostchord Tele-Holic

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    ok. sounds like the consensus is what I was expecting... remove the bridge. I have replaced a bridge once on an accoustic (and fixed the bridgeplate, and re-did the holes, still have the once used tapered cutter tool thingy) but that one already came completely off so taking this off with heat is going to be new to me. The rest of the steps I'm pretty comfortable with. Also the adjuster screws and how they work is new to me. I guess an option there is just to buy/make a new bridge?

    Thanks for all the advice!

    p.s. I did mean to say AR glue not PVA. Getting my glues mixed up. I have the right glue so that's fine.
     
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  12. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    There are several variations of the adjustable bridge thing. The idea is good - quick and easy action adjustment - but most of the time there is a lot of slop in the fitment and the feeling that that can't be good for transmitting energy from the string to the top. The "fix" however is somewhat daunting - fill the saddle slot with a piece of ebony or rosewood and route a new slot. That really isn't a do it yourself home project.

    Here is a guitar that was missing one of the adjusters - the owner asked me to convert it

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    The problem with replacing the bridge is that the ones I've seen don't fit the Martin or Gibson footprint so you are looking at making a new bridge - not an impossible task but not easy either.

    I would approach this one step at a time - reglue the present bridge, make sure the geometry is OK, see if you can get the action where you want it with the stock adjustable saddle. Play it and see if you are happy with the sound. If not consider filling and slotting the existing bridge.
     
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  13. Boreas

    Boreas Poster Extraordinaire

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    You could try an "oversized" Martin bridge. It would likely cover the footprint. Hard to tell without measurements. I don't think I would bother making a bridge if it is an inexpensive guitar unless you just want to try it.
     
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  14. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    The problem with replacing the bridge is that if you buy one with the saddle slot already cut that becomes your index for where to install it - center of the high E string at the scale length plus whatever magic compensation you use, same with the low E string. Since the saddle slot may not be in the same place on the bridge that shifts the bridge. Since the holes may not be in the same place that shifts the holes. The hole spacing might not be the same (even Martin has differences) - the whole thing is a crap shoot.

    Find someone with a saddle slotting jig like mine and put the saddle where it belongs.
     
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  15. magicfingers99

    magicfingers99 Friend of Leo's

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    try some neodmydium magnets from amazon, they make might fine clamps. Apply a wet paper towel to the bridge after removing the strings. Heat the area of the bridge that has lifted with a soldering iron applied to the wet paper towel.

    basically the wood is distorted, (bent) from the string pressure. steam will help it return to its natural shape. wet heat in the basis of the wet paper towel and soldering iron will work but its slower than steam. take your time. its not a race and it won't straighten out as soon as the iron touches it. you will need to heat and stop and repeat. you want to induce change into the shape of the bridge, without scorching it.

    when the bridge is reasonably flat, use water thin superglue - apply slowly and mask the top around your work area. once
    you have glue under the area, clamp it with the neomydium magnets.

    test the clamping process BEFORE you glue to make sure the magnets will apply enough force to clamp the joint closed.
    clean up the excess glue while its wet.

    https://www.amazon.com/neodymium-magnets/s?k=neodymium+magnets&tag=tdpri-20

    switch to a lighter gauge of strings to lessen the chances of this happening again.

    if it fails, acetone can be used to remove the superglue. and try again or .....
     
  16. popthree

    popthree Poster Extraordinaire

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    i bought some pretty decent clamps from Harbor Freight for super cheap... not sure if that store is in BC or not though
     
  17. FMA

    FMA Poster Extraordinaire

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    I would recommend spending some time looking around Frank Ford's site, frets.com, a great resource and Frank has a great sense of humor.
     
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  18. envirodat

    envirodat Tele-Meister

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    I am just starting on a bridge project and Freeman had pointed me to this post. I got a guitar from Goodwill and when I got it, I found that the bridge was lifting
    [​IMG]

    I figured this would be a good time to learn how to do a bridge repair. After reading Dan Erwines book and watching several videos on how to take it off, I was ready to try. So step 1 was to take the strings off. What did not expect was that when I pulled on the bridge pins the whole bridge would come off! So much for worrying about putting too much heat on it while trying to take it off.

    upload_2021-11-4_9-24-40.png

    Looking at it, even I, a complete newbie, could see they glued the bridge on the finish.

    Looking at the top of the bridge I saw some glue marks as well.
    upload_2021-11-4_9-27-10.png

    I looked at the bridge plate underneath. To me it looks good.
    upload_2021-11-4_9-34-48.png

    It makes me wonder if the guitar was used until the strings pulled off the bridge. It was made in 12/77.

    Time to get moving the next phase of the project.
     
  19. Gsweng

    Gsweng Tele-Meister Silver Supporter

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    So far, so good. This should be duck soup, as one of my old profs used to say!
     
  20. Texicaster

    Texicaster Friend of Leo's Ad Free Member

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    As said above.....

    A pro should do it for ~$100-$200 but may take some time IF you can find one locally.

    BUT it CAN be successfully reattached without removing! With caveats!

    Yours doesn't look like a clean separation but only you can tell. Get your feeler gauges out and "map" how much has pulled loose. Feel how clean it is underneath with a real thin one.

    One of THE BIGGEST folk tales in luthiery is "titebond doesn't adhere to titebond? which is in fact FALSE! Check the video below! The conclusion is Titebond to Titebond is STRONGER that wood to wood! ~40% stronger! That's all considering a clean smooth surface which is difficult to prove without removing the bridge.

    I scoured the interweb when I had an issue a while back and could find exactly ZERO failures from this approach and dozens of success stories!

    But circumstances dictate! IF you can feel splinters under there your chances may be less.

    You also need to clamp properly. Using a couple bolts for clamps wont cut it. You need to craft a caul to fit inside over the bridge plate and have a caul on top that will evenly distribute the force. The wings are lifting on yours and those hardest to get even pressure due to curve. There's some interesting bridge clamp block for ~$20 on Amazon. Stew Mac has real nice metal one for ~$75.

    Use Titebond. NO CA or epoxy! TITEBOND #1.

    Here's that video comparing gluing surfaces.

     
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