Repair And Restoration
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Yet another bridge re-glue question…
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Yet another bridge re-glue question…
I had a customer contact me and he told me that he has a Zager ZAD80CEOM and that the bridge is staring to raise at the back. He says the gap is about 1/32″ and would like me to remove the bridge and reapply it. I have yet to see the guitar in person and I’m a bit hesitant to take it on. I’ve never performed this type of operation before, although I do have some theoretical knowledge of it, just not practical. Some of the question I have include things like where should I go to find the knowledge about this type of thing? What glue should I use and what do I do if the top have a belly to it? How will I know if the bridge does in fact need to be removed and reapplied? I feel a bit lost when it comes to specifics and advice on what to do here would be appreciated.
This does lead into a larger question however. I’ve been doing guitar repairs for about 15 years and I feel like my knowledge is skewed more towards electric guitars vs. acoustic. Where would you suggest I learn more about acoustic guitar repair theory? Are there any books you would recommend? I realize that some practical work would be useful in addition to theory and I have a couple of acoustic guitars that are in very rough shape that I’m planning on rehabbing.
-David -
12 Replies
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Nothing can be determined until the guitar is on the bench. The customer’s 1/32″ could actually be a 1/16″ or more likely .010″. No one can give opinions, advice or estimates until the guitar has been evaluated. I would start there. Alot of times people call for pricing or other questions to waste your time and you never hear from them again…
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Hey Dave, that sounds like the best starting place. I am jumping the gun a bit here and spending mental energy on something that may turn out to be a non-issue. In the meantime, I would be curious to know of suggestions for learning about acoustic guitar repair theory either through books or videos if you or any of the other members have them. Thanks for the response!
-David
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Oh it’s been a while. 30+ years ago there were not many resources available. I had Complete Guitar Repair by Hideo Kamimoto. (I think we all did) It’s still a great starting point. Dan was just barely getting going on the VHS videos and books in the early 90’s.
Can’t seem to post the links but there are great videos on StewMac’s Trade Secrets page.
Probably a lot on YouTube but you’ll have to use your best judgement there (I’m thinking)
You’ll either need a heat lamp (and a way to protect top with carboard wrapped in tin foil) Or a heating blanket to heat the bridge to approximately 240 degrees. And a thin sharp spatula. Gotta pay attention to grain run out. And try to determine if the bridge may have been finished with lacquer, poly or who knows what. (that all can be repaired if things go sideways) You’ll need some cauls for both inside (triangle shaped to fit the crotch of the X brace and thick enough to be as tall or taller than the braces depending on the clamps being used) and outside to protect the top of the bridge. (most of us make these as there are no universals) Other than that it’s pretty straight forward. Remove bridge, clean surfaces for best adhesion and reglue.
Bellied tops can get more complicated, I’d cross that bridge when you come to it. There are specialized cauls for this. If it’s not bad I’d leave it some bellying is expected on all acoustics. (and I wouldn’t bring it up with the customer unless they do first, could open a can of worms) Almost all acoustics have a radius in the top and are not truly flat.
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I just looked up this model you referred to. It supposedly has a solid cedar top. These can have issues as sometimes the bridge isn’t lifting it’s more the cedar is coming apart from itself. Especially if the guitar has been dried out excessively or gone back and forth between humid and dry conditions. Again, gotta get it on the bench first and go from there…
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The customer stopped by and we chatted for a bit about the guitar. He bought it brand new in 2020 during the pandemic. I wasn’t sure what to expect but upon inspection the bridge is certainly lifting off the guitar and will need to be reglued. The first thing I did was detune the strings to take tension off of it, this seemed like a logical course of action. I checked with some feeler gauges and there is about a 1/32″ gap around the backside of the bridge, and this extends roughly a third of the way through the bridge. Upon taking the feeler gauges out of the bridge, there was some debris that came out with it. I’m not sure whether or not it was glue or finish. I also took a straight edge and laid it parallel behind the bridge and noticed a hump in the middle and gaps on either end. I haven’t yet measured how much of that gap there is or whether it’s significant.
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Here’s one other photo of the bridge.
So my main question is how would you proceed with this? Any more thoughts from you Dave Staudte @patreon_94549210 ?
In addition, the customer also mentioned wear on the first few frets on the treble side. I took a picture and I couldn’t help but feel like this is a fairly excessive amount of fret wear for a guitar that’s from 2020. I’m going to ask the customer how much he plays but what I do know is that he played when he was younger and only got back into it over the pandemic. He’s a retiree, he doesn’t play live and I don’t get impression that he’s spending hours a day playing, although I suppose it’s possible. This leads to a question of mine, is it possible companies are using inferior fret wire? recently, I feel like I’ve seen some very heavy fret wear on guitars that are practically new.
Anyway, I’m looking forward to hearing back from you all. Thank you!
-David
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That Definitely needs a Re-glue. My method is to always scribe the bridge with a sharp xacto blade before removal and “pocket” or recess the bridge slightly into the top by removing any finish that had extended under the bridge when it was first put on. I use a Dremel 115 bit and a chisel to get a fresh flat gluing surface, then sand the bottom of the bridge to make contact all across the new surface. then just titebond 1 with 3 bridge clamps and good glue cleanup practice. (titebond is water soluble if you don’t get it all). I also wait 2 DAYS before applying string tension to anything that I use wood glue on. also don’t forget to put a piece of tape under the bridge pin holes so you don’t get glue inside the instrument.
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Those are good pictures; it looks like it’s not the cedar separating from itself scenario. But you’ll find out. Pull and reglue.
That fret wear is needing a partial re-fret in my opinion. And everyone wears frets differently. I have a friend who gets no fret wear at all because of his light touch and I’ve seen other players that need partial re-frets and sometimes whole re-frets on an annual basis… Usually not the fret materials fault. Although some wire is better than others.
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Alright so I spent some time tonight removing the bridge. It was pretty slow going and I have a feeling I know why. I think they used epoxy to glue down the bridge. While I’ve never removed a bridge before, I have removed fretboards and in my experience they usually come off without too much trouble. You can sort of ease your way though the glue with a little bit of muscle. This felt like guiding a knife through glass shards, not gummy at all but more stiff and chunky. Any thoughts on whether or not this is likely the case?
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Here’s the end result. Overall I’m pleased with how neat a job I did, there was no damage to any area other than underneath the bridge. The area is relatively flat but there are some chunks of wood taken out and I’m reasonably confident the manufacturer sprayed the entire top and epoxied the bridge on top of it. Do you think this is a correct assumption?
As for the area under the bridge, I could use some advice on how to proceed next. I know that chisels were mentioned, as well as a Dremel to flatten the area before placing the bridge (which will also need to be flattened). I like the idea of a Dremel but with the top being not perfectly flat, how would one proceed to use the routing tool while staying level? Also, I’m assuming it would be good practice to use wood filler to filler the missing chunks taken out as opposed to anything else?
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Last pictures the night, this will need to be addressed. The bridge plate and bridge pins are both fairly chewed up, I’m guessing replacement bridge pins at the very least or more ideally, new pins and a bridge plate repair/replacement of some kind. Any thoughts here?
Thanks for the help guys! I appreciate it!
-David
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Hey folks, I’m making this message a few days after my last to see if anyone has further insights. Here’s where I’m at with it. I’ve continued to work on the guitar and I got the underside of the bridge surface to be completely flat. I began sanding/chiseling the guitar top where the bridge lays and I think the best course of action at the moment is to mechanically remove the finish/glue. By the way, I was thinking that the glue was epoxy, I’m now considering that it’s in fact super glue. Anyway, the finish is quite thick where the bridge lays and I think that in order to remove it by hand I would be spending an enormous amount of time doing it. My concern though is that the Dremel/router method runs the risk of chipping the finish, which would open a whole other can of worms, one which I’m not set up to deal with. I’m thinking of informing the customer of my progress, letting him know of some other concerns that could and perhaps should be addressed (bridge plate), and also letting him know that there is the risk of the finish being damaged and the possibility of a partial refinish. Hope to here from you all again, perhaps from @Riley_guitars or @patreon_94549210 or someone new would be welcome as well. Thank you!
-David
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