What type of over everyday glue for acoustic bridge.

Discussion in 'The DIY Tool Shed' started by robert donithan2, Sep 4, 2021.

  1. robert donithan2

    robert donithan2 Tele-Holic

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    IMG_20210904_103000861.jpg I only paid $99 for an acoustic/electric guitar(new-amazon). After 2 years in a damp environment the bridge glue is starting to stretch leaving a gap where I can seep some glue while under the strings tension. Then I can loosen the strings and the bridge will go back to where it was-i tried that part., but I don't know what glue is best for tension..any suggestions?
     
  2. jfgesquire

    jfgesquire Friend of Leo's

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    Remove the whole bridge, clean off both surfaces and reglue with Titebond I and clamp using the correct hardware.

    Cheap to buy the cauls and clamps yourself and learn on a $100 guitar.

    I'm sure others will point you to good "how to" videos, but I'm on my cell phone, so...

    If I could wager money... I would bet the bridge was glued onto finish.

    The finish needs to be removed to the footprint of the bridge.

    If that's a plywood top, I hope the plywood didn't split.


    The finish/color doesn't look too bad from that angle for a $100 guitar
     
  3. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    Exactly as Jfgesquire says. Remove the bridge entirely. I use a silicon heat blanked and an artists pallet knife

    IMG_1088.JPG

    You may find all sorts of different things when you get it off. Ideally it comes off cleanly, but often you will have some fibers of the top spruce still glued to the bridge. Unfortunately a common thing is that the finish was not completely removed from the top before the bridge was glued on

    IMG_1089.JPG

    Your goal is to get every bit of that old glue off of both the top foot print and the bridge. Chemical stripper works on lacquer but not very well on catalyzed finishes, you'll have to resort to scraping and sanding.

    IMG_1093.JPG

    The next thing to do is sand the bottom of the bridge to the contour of the top. Just lay a piece of 80 grit on the dome of the top and sand the bottom of the bridge

    Next you need to make some sort of clamping caul for the inside of the guitar. It needs to sit up against the bridge plate and keep the clamps from crushing the X brace. Remember that glue will thru the pin holes and glue it in place if you don't cover it with waxed paper. I made a couple out of UHMW for different bracing and pin hole locations. The t two machine bolts and wing nuts positions the bridge relative to the pin holes and applies some clamping force

    IMG_1096.JPG

    Depending on the exact shape of the bridge and location of the braces I usually use three clamps along with the bolts. Remember that the bridge wings are over the X brace, you want to carefully clamp them without crushing the brace. Use some sort of cauls on top of the bridge to avoid damage

    IMG_1098.JPG

    Use AR glue (original Titebond) or hot hide (which I'm sure you are not set up to do). No substitutes - if you ever have to get it off again those will release.

    After the glue has dried drill out the pin holes with a 3/16 bit, then ream them with a tapered reamer to fit your pins. Make a new saddle, string it up and open a nice cold adult beverage.

    IMG_1100.JPG


    I'll add one more comment - this is the most common failure and repair I see on acoustic guitars and it should never happen in the first place. Too many of these guitars have finish still on the top - glue does not stick well to finish. Some of these guitars get left in cars on a hot day - I use heat to separate glue seams - duh. Often the owner tries to fix it them selves with a little mystery glue and maybe a couple of screws - the more they muck it up the harder it is for me to fix correctly. Often there is a lot more damage to the top than I show in the above picture - that needs to be dealt with on a case by case basis.
    Short story, learn how to do this correctly and you will have all the business you can possibly want.
     
    Last edited: Sep 4, 2021
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  4. guitarbuilder

    guitarbuilder Telefied Ad Free Member

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    Take an xacto knife and score the finish around your bridge before you remove it. Then after it is off, take a sharp chisel and scrape inward from those score marks until all the finish and glue is removed and you are down to bare wood. Hot hide glue would be ideal but most don't have access to it, so titebond one will do the job. Don't use any other titebond formula. Use a caul and several clamps to glue the bridge back. Put a block inside the top so that area doesn't get crushed and also the clamps will fit better. After the glue is set, you can clean off the squeeze out with hot water and paper towels. Diluted lacquer could be applied with a pipette around the bridge if you want to fill in that gap. Frank Ford does an excellent job of a lot of these types of repairs.


    FRETS.COM
     
  5. Vizcaster

    Vizcaster Poster Extraordinaire

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    I hope that by "over every day glue" you don't mean just anything that you have lying around. Titebond (original, red label) is perfect so long as it's not a stale bottle. The other Titebond II and III so called waterproof glues are runny and not as tacky and, well, they're just a solution in search of a problem. If you're actually gluing wood then Titebond (original) is the best wood glue. Then again if you're going to invest in bridge-clamps and a bridge pin hole reamer, then you might as well pick up a bottle of fish glue (which is basically a step between Titebond and hide glue because fish glue comes in a bottle already in liquid form and doesn't need a hot glue pot). Like hot hide glue, fish glue is easily reversible with heat if the bridge ever needs to be replaced (or if the repair fails).

    It's been said already here but it bears repeating - the bridge must come off before it can be glued back on. Dollars to doughnuts the finish is still there in places or perhaps under the entire bridge. Score around the bridge with a fine scribe or a marking knife before removing it in order to give yourself a line up to which you're going to scrape the finish. Un-gluing what's left can be as simple as using a heated palate knife. Remove any finish that remained stuck to the underside of the bridge.

    As pictured, you will need long-reach C-clamps sold for this specific purpose, but you don't need pre-made cauls those you can cut and shape yourself. Some sort of mirror is also necessary so you can see where you're putting the clamps inside. Also I find it helpful to use sacrificial nylon alignment pins in the bridge pin holes to make sure the bridge is being clamped down where it belongs and won't shift as you tighten things up.

    The reason why it's necessary to ream the bridge pin holes is that some cheap guitars are made with un-tapered pin holes, so you need to clean them up with a 3-degree or 5-degree tapered reamer (again a specialty tool for bridge pin holes, not the same taper that's on a machinist's reamer), that way through the life of the guitar the player will be able to simply replace the pins with commonly available Martin brand pins. When you compare them to the thin pins that come with some cheap guitars you'll see the difference.
     
  6. jfgesquire

    jfgesquire Friend of Leo's

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    I am FAR, VERY far from being an expert at anything, and your advice is excellent, of course, but I have concerns about scoring with a blade around the bridge. If you cut too deep, you'll cut into the wood fibers/grain and now you'll have short pieces of guitar top that can tear off even easier because they have a place to start. Any scoring can only be as deep as the finish and no deeper.

    I think it was either in a Frank Ford or Dan Erlewine video I saw it mentioned.
     
  7. Freeman Keller

    Freeman Keller Poster Extraordinaire

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    I don't score around my bridges. You can see in the forth picture above that I have left a little ridge of finish around the edge of the bridge foot print. I put a very small channel around the edge of the bridge to fit over the finish (different guitar, I've got lots of pictures of failed bridges)

    IMG_4774.JPG

    One more comment, when I go back to the first picture it looks like maybe someone has already tried to "fix" it by forcing some sort of mystery glue under the bridge - maybe polyurethane. If so it all needs to be removed, that just makes the task a little more difficult.
     
  8. Vizcaster

    Vizcaster Poster Extraordinaire

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    Thanks for pointing that out, what I was talking about was only making a mark not cutting. A marking knife, or better yet a scribe from a hobby shop with a terribly fine point, will be more precise than using a pencil. My concern is that when the bridge is off there might not be as clean a shadow to follow when you do start scraping the finish.
     
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