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I'm about to install the bridge on my latest project. In my seven prior projects I located the bridge and used Ibex clamps (or what Grizzly sold me, copies) to clamp the bridge to the soundboard. Kinda clunky, commonly used, did the job. No failures (except for the painless bridge that chose to go walkabout).

Before I built anything I bought, but have never used, a 'guitar bridge clamp', a doodad that clamps the bridge in place with bolts through two bridge pin holes and uses two similar bolts to push down on the bridge's wings. I'd like to use it if it works, if for nothing else than the experience gained from using new-to-me tools and fixtures.

The current installation is for a rosewood pinned bridge attached to a cedar soundboard.

Is this kind of bolt-on clamp capable of doing the clamping job well?


Thanks!

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Peter Havriluk

Is this kind of bridge clamp you are asking about? I have two sizes of this clamp, one for guitars and one for octave mandolins and mandocellos. I've used them on all my instruments with no failures. The 5-course mandocello I finished early this year has 295 lbs total string tension and it's doing fine.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Yeah, that's what I'm talking about. Functionally identical (Mine's anodized, there's thumb wheels where yours shows cap screws).

Underneath, mine doesn't have a full-width caul, just a plate under the pinhole section of the bridge. Is that common to this style of clamp?

And do you feel there's any advantage to using this clamp, save it takes up lots less room and cleaning up glue squeeze out is easy? I have some unease about how firmly the wings get clamped down.

Thanks again.

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Peter Havriluk

Some time ago I made a couple of cauls out of UHMW (cutting board material). It fits inside the X and has two slotted holes that I can put 3/16 bolts thru the caul and outside pin holes. I originally made them for regluing bridge but I now use them for new builds too. Glue doesn't stick to UHMW, the slots allow it to fit different pin spacings, the bolts do apply some clamping pressure but I also add three traditional clamps. If you notice the bolts are really machine screws but I added a nut against the head which allows me to reach in with box end wrench and unscrew them if/when they get glued in place.





I have an autocadd dwg file of the caul in case you want to build on, any machinist can mill UHMW

ps- for the outside of the bridge I just use three little pieces of wood to pad the clamps.

I don't have a caul under mine either. I fit my bridges exactly to the curvature of the top so I haven't seen a need for one particularly with the bridge plate there. And none of the bridges I've installed have lifted. I don't know if it's common to not use a caul inside.

I agree with the advantages of taking up little storage space and easy cleanup of squeeze out. It also installs quickly.

There's no problem with getting the wings clamped down firmly. In fact, you can overdo it if crank down too much.

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Once in a while you get shown the light in the strangest of places if you look at it right - Robert Hunter

Gonna try out this toy!

Thanks very much.

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Peter Havriluk

So one of the most important elements of if your clamp will work Peter is what glue you intend to use.

My answer to will your clamp work OK is no if you intend to or would like to use HHG to glue your bridge. You can make this clamp work for HHG but it's more difficult and you never really know when you do miss the time constraint until some years later when it lifts in the middle of the night....

These kinds of clamps and their variants require too much time to set the clamp to use HHG in my experience. If you are using say Titebond Original which I would not use for bridges since HHG is a better choice the clamp is fine.

For those of us who use HHG we preheat but still try to have everything in place in 15 seconds or less and snugged down. It's not hard to do either with the right planning, set-up and things prepositioned.

HHG is a pretty hard to beat adhesive for bridges and it's also what the market seems to appreciate too.

I've reglued more bridges that someone used the wrong clamp and glue combination than my old mortgage before I paid it off can count. We always used HHG, clear the footprint very well to very close to the perimeter and used an Ibex clamp with the bridge caul with a dimple in it. Fitting is key and when well fit a bridge and top does not require two additional clamps for the wings which I often do anyway if there is any question of the fit. All three clamps in a worse case situation are prepositioned with the middle one already in place and suspended on blocks with masking tape so all I have to do is twist the tensioner.

It's rarely mentioned here these days what we always talked about 15 years ago on the OLF and that is that HHG, Fish too but we don't use it or trust it..., HHG will draw parts together as it cures unlike say Titebond Original. With this said clamps are of course still required and I would also advocate for spending all the time necessary to get a perfect fit with only light finger tip pressure on the wings. But the ability to draw parts together is one of the hallmarks of why HHG has been the Lutherie glue of choice for well over 100 years.

So when you ask what clamp I ask what glue. Hope this helps.

Hesh, thanks for bringing in your experience and judgement.

As for glue, HHG for me imposes too many 'gotcha' constraints involving the clock for me to feel comfortable using. Lately I've used 'Titebond extend' and I don't feel rushed. I do match-sand the bridge to the soundboard so that I get full contact between the surfaces before clamping. I can do a bunch of trial fits before breaking out the glue, so that all the motions and inspection points are considered. Not being on a job associated with production or payment, I can take the time I need without begrudging it. I intend to clamp it up and go to sleep...

Thanks again!

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Peter Havriluk

I’ve been using 315g HHG and a vacuum clamp for my bridges. The vacuum clamp is quick and easy. For me, it has been worth the expense.

I've been using Old Brown Glue instead of HHG when I’m feeling time constraints will not let me work fast enough to get things done in due time with HHG. From what I gather I believe it's HHG with the addition of a retardant such as urea. Anyway, works fine and I'm just a bit more confident in it than in fish glue for bridges. My 2 cents.


Pierre
Guitares Torvisse

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Pierre Castonguay

Will wonders never cease? I went to use my shiny and unused clamp, and surprise, surprise. The threaded fasteners meant to go through the E/e bridge pin holes are 5mm, not 3/16". While a metric converter will tell you that 5mm converts to 3/16", it's ten thousandths of an inch too fat. I think maybe that this device isn't U.S. made.

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Peter Havriluk

Cool and thanks for this Peter. Titebond Extend which always sounds like a marital aid... is an excellent glue and good choice for your situation.

HHG is NOT a good choice if there is ever a question as to if someone can follow the required short open time constraints so good on you Peter for respecting this and going with an alternative. Your clamp should be fine for Titebond Extend and again good choice. We've used it too and liked it.

Hey Pierre I hope you and the puppies are doing great!

We will have to try Old Brown glue and yes we've heard it is a variant of HHG too but with additives to keep it liquid longer. Good information thanks my friend.

Maybe drill 5mm holes in sacrifice boards and see if that can still be reamed with a 5 or 3 degree reamer to snuggly fit a typical bridge pin. Might still be OK, might not.

If installing bridges on new guitars, the expectation should be a near-perfect joint, so very low glue-line clamping pressure might be acceptable, provided the clamping system does not itself distort the bridge/top joint. For repair work, joints are never perfect without radical, often unacceptable modification to the top and/or bridge, so relatively high, evenly distributed glue-line clamping pressure becomes one of the two key factors in determining longevity of that joint.

Judging from the multitude of issues involving bridge failures and partial separations I saw at Greenridge and in the much slower-paced work since then, joint perfection, and therefore glue line pressure is an issue for both factory and custom builders. In other words, the expectation of joint perfection for a new instrument is often unrealistic, leading to those years-later service calls. The reality of what shops such as Mr. Breakstone's see in the door suggests that higher clamping pressure and more reliable adhesives should play a role in both new construction and repair work if bridge joint reliability is of interest to the builder and repairman. Further, the method by which clamping pressure is distributed across the glue line becomes of greater interest as joint quality deteriorates.

To pick on Mr. Breakstone's shop again, I suspect that Ann Arbor's experience with adhesives mirrors my own, with a experiential base that acknowledges that, while nearly any wood adhesive MAY work, the caveats associated with anything other than HHG or an aliphatic resin or modified PVA adhesive (AR/PVA) rule them out for bridge work. Further, the required very thin glue line needed for a reliable AR/PVA joint make either very high clamping pressure (minimum of 150 psi, with closer to 300 desirable on really poor joints) or joint perfection a functional necessity. As Mr. Breakstone mentioned above, HHG tends to have some characteristics which allow more deviation from joint perfection while still retaining an expectation of bridge-to-body joint longevity, but here too, clamping pressure and speed at which the joint is closed come into play, because ultimate glue line thickness is important here as well,

Other issues?

- Wood moves when wet, and any of the glues we use add water to the joint. The assumption that the new installation joint will remain perfect - and therefore suitable for a low clamping pressure glue-up - once the top and bridge are wetted out may be unwarranted. In general, either HHG or AR/PVA application will expand the mating surface of the bridge and top, leading to a reduction in bridge radius across the top and increase in radius on the body axis, while the top will increase radius across the width of the top.

- Additionally, one luthier's notion of joint perfection is another's barely adequate fitment. Experience matters, as Mr. Hall's oft-expressed aphorism applies here: you don't know what you know until you know it.

- Finally, clamps and cauls have some impact on success of the joint. A vacuum clamping system will never generate more than local atmospheric pressure-level clamping force minus a few PSI, so maximum clamping force over the roughly 7.5 square inches of a typical Martin-style belly bridge patch will be less than 100 pounds, or less than a tenth of the recommended MINIMUM glue line pressure for Titebond on a mediocre joint fitment. For the combination of two Ibex-style clamps and two cam-style Klemmsia clamps, that applied force might be closer to a minimum of 1000 pounds, or about 130 psi - still below the 150 psi Franklin suggests for mediocre joints, but sufficient to address much of what we see in everyday repair work. Cauls matter as well, with the lack of them occasionally being responsible for inducing top distortion or even damage in the form of cracks (e.g., the older-style Stewmac bridge clamp wing issues). Cauls ensure both efficient distribution of clamping pressure and support for often delicate surrounding structure.

Before this drags on too long, at Greenridge, our preferences mirrored those that Mr. Breakstone expressed: HHG (in a pinch or if the customer insists, Titebond) and a clamping and caul system capable of thinning the glue line to a uniform thickness of under a mil, and doing it quickly enough to avoid premature gelling of 315g HHG. Those lighter-weight clamps discussed earlier in the thread do not generate the 300 pound (min) force seen from an Ibex, nor the 200 pound or so force seen from a Klemmsia, so are a bit more of a gamble for repair work or where joint perfection is an issue on new bridge glue-ups.

There are other threads that cover the method to address HHG's gel time constraints. Suffice it to say that the combination of a warmed bridge, the right clamps and cauls, and adequate preparation allow a fairly leisurely, unrushed approach to the job.

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For the times they are a changin'

- Bob Dylan

Just speaking for myself (we all have our preferences):

I use hot hide glue for bridges; in fact, it is the only adhesive I use for parts that stay on instruments (Titebond and CA glue are useful for jigs, etc.). I have tried a few versions of the “bolts through string holes” bridge clamping caul. However, I prefer using 3-4 of these clamps:

https://www.stewmac.com/luthier-tools-a ... le-clamps/

They have leveling feet that allow you to roughly position them before spreading the glue, then finally position them very quickly, once the glue is spread and the bridge is in place. They are thin, so you can fit a number of them in the soundhole at the same time. They work very well for me.

I think an important difference between my clamps and the bolt-through caul is that, with the bolt-through caul, the pressure being placed down on the wings is both interactive with the pressure on the middle of the bridge, and it is only a downward force on the bridge, with no matching upward force on the guitar top. In other words, clamps pinch two pieces of wood together, whereas the bolt-through caul only provides such pinching in the middle of the bridge, not at the wings. At the wings, it just pushes down, without something also pushing the top up.

Does that matter? I dunno. All I know is that I perceive better, stronger, and faster (think Steve Austin) clamping pressure on the bridge by using several of the above-referenced clamps spread across the bridge.

Pretty much what Don just said. I also use the same clamps. With a bit of masking tape they’re easy to pre-position for a fast glue up. This one was a repair but I do the same thing on new builds.

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Steve Smith
"Music is what feelings sound like"

For Titebond, you might need 150 psi. For a well-fitted HHG joint, you don’t. I quit using screw and cam clamps on bridges when I realized they were causing distortion at times, weakening the joint.

Sometimes there's merit to letting stuff mature a bit before committing to action. I honored my shop rule of no work after ten PM and went to sleep. Now I have a whole bunch of very helpful points of discussion about clamping and gluing bridges. I'm going to honor past positive experience and put my Ibex knockoffs to work. I think I was edging toward overcomplication in a search of simplicity. No need.

Thanks, everybody!

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Peter Havriluk

As I mentioned, a well-fitted joint - my near perfect joint - is usually not going to be an issue for any glue - the glue line will be a thin one even where very low clamping pressure is available. It's really more my concerns with less than perfect joints and those really suboptimal joints seen on some vintage instruments.

Re: 315, it seems like even a thick glue line holds with vigor, and it's the only glue we routinely clamped for 6 hours, then put a full load on the bridge shortly thereafter. Once the technique is learned for getting around the higher gel temperature (warm the bridge patch a bit... heat the bridge to 135-140 deg F... allow the bridge to act as a heat reservoir when the joint is closed). For other glues that do not have structural gap-filling properties - Titebond included - it's really all about getting enough pressure on the joint to close the joint and get a thin glue line.

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For the times they are a changin'

- Bob Dylan

Great thread!
Beau Hannom showed an extremely useful method of locating, using masking tape block locators, cut from a roll of common masking tape. I've used ot to locate bridges with excellent results. I use this extensively for all manner of locating tasks. The masking tape method starts at 2:10:
https://youtu.be/VfCI95jEBpQ?feature=shared

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Measure Twice,

Karl Borum

I have always used Titebond original to glue my bridges (and many repair jobs) for 50 years-never had a problem.

I use the Stew Mac caul and one strong Pony brand deep throat clamp.

Great post Woodie.

I hated using the beefy aluminum fine thread clamps. As well as the SM steel ones. Both made me think an accident was soon to happen and they just seemed clumsy and slow. I made some long reach cam clamps that were thin enough to fit 5 easily thru the sound hole and light enough and smooth edged enough to not be scary to use over a guitar top.

I try to follow instructions especially glue and finish but I think 150-250 psi on a wood joint like a bridge to a thin spruce top seems crazy excessive.

I'd rather have equal pressure on top of the bridge and under the top and good support along the bridge.

I make cauls out of high density styrofoam glued to a strip of 1/8 hard board. Both give a little to compensate for irregularities without breaking something. I use HHG.





I made a 3/4 thick mock bridge out of cherry and I heat that up to around 200 F and set it in the footprint of where the bridge goes and it does a great job of heating just the area where bridge goes without worry of messing up finish or getting too hot. Heat the bridge too.

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Brian R, Wood Mechanic
N8ZED

Wow, this is an interesting thread and I just got around to reading it. I can't wait to see my Titebond glued bridge start lifting. Seems like I should only be using 315 gram HHG for installing bridges or using extreme clamping force for Titebond. I have no idea how much force I applied and have no way to measure it. On my first guitar which I finished a couple of weeks ago, I used Titebond and 3 HF deep clamps, I don't remember the actual throat size. I used 192 HHG on my Gibson rebuild I did many many years ago and haven't see any signs of lifting on that.

My brothers 20 year old Martin is showing some lifting. I wonder what they used.

In spite of my somewhat snarky response here, I will get some 315 before my next bridge glue because in spite of evidence to the contrary, though stupidly small control group, I'll bow to the gods that have more experience and give that last ounce of security to my next bridge.

Maybe get some fish glue to round out my gluing obsession.

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Hutch

Get the heck off the couch and go build a guitar!!!!