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I just had a bridge come off on a new build. First time ever having any failure to any degree gluing a bridge. Started lifting as I tuned it up for the first time, so I back tension off immediately, and was able to separate the bridge the rest of the way by hand with a seperation knife, with no heat or pulling of any top wood. I had good squeeze out as usual so I believe I used plenty of glue..Stew mac bridge caul and ibex clamps . EIR wood for the bridge. Nothing new...except the glue used this time ( and for the first time) was the LMI new formula yellow color stuff.

Anyone have glue failure attributed ( as far as you know) to this glue. I don't see so far that I did something wrong on my part. So far.

michael

Doesn't sound good to me. Did you have a freshly scraped joint?

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

A mystery to be sure

Yes....fresh wood to wood. Inspection of the two surfaces, sure looks like glue failure to me. LMI says this is the first they've heard of this problem. Ya right.

I haven't used the StewMac bridge caul but I have used the Fox bridge clamp from LMI which is similar. I have had glue failure each time! Here's what I think is happening. When I screw down the edge screws this causes the bridge to bend a little bit and to lift up in the center. This lift up is too small to see but I do notice that I don't get much squeeze out except at the edges. I've since put the tool away with "doesn't work, do not use" marked on it less I forget and try to use it again.
Remember that this is with the Fox tool from LMI which uses built in screws instead of the center clamp.

Braz, I think some very simple glue testing would be in order before accusations are made.



1. What kind of glue are you using?
2. I doubt if the center was clamped down tight that you would get any separation from tightening the ends. Although, you might get a little unwanted curvature of the whole area.
3. Where else would you expect to get squeeze out, except for the edges?

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Pat

Very rarely is it the fault of the glue. In my opinion, these are the "usual" culprits in order of importance.

1) Parts do no fit together well
2) Inadequate or improper clamping
3) Surface contamination

During the bridge gluing process, you really want to closely evaluate all 3 of these potential issues. A post above mentioned testing the glue with a test joint and I agree. If there is a problem with the glue, then it will not work but if it does, then you know that there is an issue with your process. I'd recommend using an oily piece of Indian Rosewood and a piece of spruce to duplicate your bridge joint as closely as possible.

If the new test joint fails, let everyone here know as that information is useful for the lutherie community.

Tell us about your joint.

Gloss finish? How thick? Is the finish removed all the way around the bridge, as if it were inlaid, or is there a ledge underneath? How big is the gap?

Pictures of the failure would be very helpful to analyze the problem. Sadly all is speculation without them. T

The finish is 4 mils at that location...1/16th (light) indent, radius of bridge matches top perfectly. Stewmac bridge caul is very effective in my opinion, with 2 clamps in the hole, don't know about the LMI one, Mike...but you had a good point , which I checked out. No contamination that I can discern .... parts fit well. I've glued the bridge back on, after freshening all surfaces...but using Titebond thus time, so I can not show pics. I did wipe the bridge with acetone this time, which I'd not done before.

Just cause...the LMI glue...goes in the Polywhey bin. So it goes.

I saw the same issue with the StewMac clamp. Unless you had a very rigid clamp on the central section tightening the wing clamps could cause the center portion to lift a bit and loose pressure. I found the Ibex clamps a little too flexible.

That said, the wings should have been well glued even if this happened and the whole thing popped off so perhaps it is the glue. Some test glue-ups with the same batch would be very interesting.

Tightbond extend has been getting some good press as a replacement for LMI white. I've used it and it dries hard and brittle like the white. Seems a little thicker than regular Tightbond. At this point it is my substitute for LMI white. I have not tried the new LMI glue.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

Not to stray too far from the original subject, but I've been using Titebond Extend on some parts (including one classical bridge) and I'm very happy with the results.

Have been using the Titebond Extend for years on other stuff. Bridges....hmmmm.

Can't......resist.........must.......say......hide glue !

1. The first two times, I started with hide glue but switched to Titebond for the re-glue. Titebond is more forgiving for imperfections in the prep or clamping. The third time, I started with Titebond but still got the failure.
2. You are most likely correct that the center was not clamped down tight. The LMI Fox clamp used screws and wingnuts to clamp the center of the bridge. These screws are located at the 1st and 6th string holes. My subsequent glue ups used five clamps with now sign of failure.
3. Sorry. I phrased that poorly. The only squeeze out was at the ends of the bridge. There was none along the front and back.

Perhaps I was a bit harsh in saying that the tool doesn't work. I guess a more accurate description is that it is easy mess up the bridge gluing process because it looks like the clamp is properly applied when it is not.

This has probably been buried into the ground so I apologize but... So is LMI white a thing of the past or what? Why the hell would they change that formula I've used it for countless years now and only have one bottle left.

AFAIK the manufacturer of LMI white discontinued it. LMI of course does not disclose their source.

This anecdote concerning the new LMI glue does not sound too promising. No squeeze out in the middle section is a probable indication of user error, but you say you got good squeeze out all the way around. Sounds like glue failure. I would do some testing on scrap before using that new glue again. Not all PVA are reliable.

The stewmac bridge thing has worked fine for me, other than not fitting every bridge shape. I've used it twice since getting it, but only with HHG. I use a thick caul underneath, and pay attention to not squeezing down the wing screws too much. Still probably provides more clamp pressure than cam clamps. I modded the caul by drilling a divot in the center, and using it with an ibex clamp with the nylon foot popped off. If you don't do this, it's not possible to use a thick and stiff enough bottom caul.

Good glue squeeze out could also mean too tight clamps. I've done it and seen it done. If you tighten clamps to much you will squeeze out to much glue thus not leaving enough to do the job. Not saying this is what happened but there's always a possibility. But for a person who has glued many things in the past knows this problem and wouldn't do it. If I were to have a joint fail I would look to the glue as well. Been there done that.

Final note : I may have over clamped Lonnie, probably not but a distinct possibility. Tuned it up to pitch this morning, several hrs now. Titebond is holding fine. All things considered....I think it was the LMI.glue, and probably won't use it again for a bridge. Just cause.

Joints fit perfect, and I use a full support under / inside caul.
I never use any glue to have strength in any gap.....been a woodworker for 35 years now.
In researching further...on the web, I'm finding others who have had a similar problem with this glue..

I think I'm going to try one of those vacuum bridge clamps, and stay with the red cap titebond..

Thank you all for the help.

Michael

No kidding. Has stood the test of time...
I have no problems with the LMI clamping caul.

Same here... HHG on all bridges and braces. Early on I had some failures using PVA glue and switched to HHG years ago and have never had one fail since. I use 3 Stew Mac C-clamps with the proper shaped cauls and clamp down just until I get squeeze out all the way around and stop. I also shape my bridges on the guitar with stick-it sandpaper using the pencil method (scribble lines on the underside of bridge and sand until they are completely gone).

Works for me every time.

Cheers,
Bob

To those that have issue with the cawl . It also takes one under it. Never assume you just use the cawl. I have a under mount that covers the entire bridge. If you over tighten the ends you deform the top .
Fish or HHG glue are my glues of choice.

Over clamping doesn't squeeze out the glue but can hinder glue flow at the cellular level. Figure about 10 lb per sq in.

If you have to force a joint , the joint isn't good. The mating surface needs to be as perfect as you can make it. HHG and Fish need clean and well mating surfaces. Tite bond is more forgiving .

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Yep. When I first got one of these about 8-9 years ago I realized during a test run that you can easily over-tighten the wings. If the bridge fits well you shouldn't have to really crank down on the wings.

I've built two guitars so far with the new formula LMI glue with no failures to date. Doesn't mean there
isn't a problem, but this is the only problem I've heard of with that glue. I find gluing the bridge to be
the most challenging glue-up in the whole process, very easy to screw up.

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Gene

Politicians and diapers must be changed often, and for the same reason- Mark Twain

If you have to force a joint , the joint isn't good. The mating surface needs to be as perfect as you can make it. HHG and Fish need clean and well mating surfaces. Tite bond is more forgiving .[/quote]

I'd love to see the proof that Titebond is more forgiving. A real example not an opinion please.

Tim