Official Luthiers Forum!

Question for the repair folks. How do you modify your bridge gluing cauls for guitars with a K&K pickup installed?
Thanks
Terry

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

You know, this issue has never come up in my shop, despite averaging one or two reglues a week. Is there some correlation between people with the good sense to have a K&K fitted also being too sensible to leave their guitar in a hot car?

Seriously though, I would either relieve the caul a few mm in the relevant locations to clear the transducer heads, or remove/replace them if I felt it absolutely had to be done to effect a good repair. Even when glued on the transducer heads can be popped off and reglued, although not 100% of the time. I have had to remove Baggs Lyric/Anthem mics on several occasions but they are trivial to reinstall due to the mounting tape used. Takamine “Palathetic” transducers and some other types unbolt to allow repairs and Maton guitars with palathetic style pickups make up well over 75% of the bridge reglues I see, 40 or more Matons a year in my one-man shop.

This is one area where it’s very much case by case basis - the approach adapts to suit the needs of the patient on the bench.

If the bridge can be made to very closely fit the top then massive clamping pressure from both directions may not be required and a”full contact” caul spanning the whole bridge footprint *may* not be necessary. But sometimes there is a poor gluing surface to deal with, or missing wood, or , or , or…

Hesh, I know K&Ks are popular in your neck of the woods. What’s your approach?

Believe it or not I have not had to reglue a bridge on a guitar with a K&K installed, yet.

So I see two possibilities:

1). Figure out where the transducers are and use maybe a 1/2" bit to relieve a sacrificial caul. May have to carve for the wires too. This is what we do for older pups from the past that were glued to the bridge plate.

2). Charge $99 more and rip out the old one and put in a new K&K Kind of kidding on this one but I do wonder how many people ruined a transducer not protecting them in a bridge reglue. At least these are not expensive pups but still excellent pups.

Good question I'll ask Dave for his ideas. I know we have removed the transducers before and it's a toss up on if that can be done safely. Some survive, some don't.

That settles it then: If you install a K&K your bridge will never lift! That's my innate ability to understand the causation correlation thing...

Josh buddy same experience on all counts here too and we have not done one unless Dave has and I don't know about it.

We super glue (Bob Smith purple top medium CA) our transducers so removal is not guaranteed or easy.

What are you doing up at 4:00 Am too

It’s 8pm here!


Sent from my iPhone using Tapatalk

Tape off bridge pin holes underneath and vacuum clamp?

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I have never clamped a bridge with a K&K installed, but here is an idea, if you don't think it will damage the contacts. You could make a caul with a 1/2" foam backing to clamp over the contacts. I make a lot of wooden cauls, with a layer of medium hard foam rubber glued to one side. The rubber layer I use is cut from some Harbor Freight floor pads that my brother gave me. Please don't tell him that I have cut the mats up to make several cauls .
A link is included below. The rubber pad will take the shape of whatever it is clamped to.
Even if you think the pressure might damage the pickup contacts, these custom cauls can be very handy for clamping anything with an uneven surface. I have even made cauls to match the shape and contours of oversized, odd shaped bridges. I just shape the rubber pad and make the contours with my band saw. The pads also make great sanding blocks for my sticky backed sand paper.

https://www.harborfreight.com/4-piece-anti-fatigue-foam-mat-set-94635.html?utm_source=google&utm_medium=cpc&utm_campaign=12192887194&campaignid=12192887194&utm_content=146847921358&adsetid=146847921358&product=94635&store=3072&gclid=EAIaIQobChMIifi_8drH_wIVWkRHAR0YGwq5EAQYAiABEgIGhvD_BwE

Winner, winner, chicken dinner!

I was going to suggest Styrofoam as well. It's stiff enough to act as a caul and would flex over the electronics. If I have to reglue a classical bridge I will make flat wooden caul with Styrofoam glued to it. I then clamp it in place and the braces make their mark in the Styrofoam. I then notch out the foam to let the braces in and clamp up. So I know it works well for clamping pressure and I bet it would work on top of a K and K. That's what I would try anyway if it were myself.

Love Chicken!

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Terry as promised we do have one and it's been used for other kinds of pups too hence the rectangular recess.

Vacuum clamping is not always a good idea in the repair side of bridge glues because the fit may not be great especially if the thing develops that dreaded crease between the pin holes.

Frank Ford was known to say he uses the biggest clamp he can find and a flat caul and he clamps the heck out of it.

We shoot for a near perfect fit with only finger pressure and then we used radius cauls and clamp the heck out of it.

And in the repair side bridges often curl and the wings need more clamping pressure than the middle where vacuum clamping can't do this either. There is also the issue of squeeze out on an existing guitar and HHG use where removing or delaying the clamping because you can't see anything with a vacuum clamp likely will violate the 15 second rule for unadulterated HHG. I know about preheating I've reglued hundreds of bridges and I do heat my bridges in my microwave along with my burrito.

So we don't vacuum clamp and prefer the Stew Mac bridge caul top side and one to three big arse clamps.

Hope this helps

Our approach was to:

1. map the bridge plate, the transducers, and the wires with rare earth magnets once the bridge is off
2. use a Forstner bit 1/8" oversize to drill the reliefs for the transducers
3. use a razor saw to cut the sides of the wiring channel,
4. remove that waste with a 1/8" chisel
5. cut the outside profile of the bridge plate caul
6. Cover the face of the caul with package tape and wax the inside of the transducer and wire channel to avoid gluing in that caul on guitars with pins (also tape the underside of the pin holes)

This takes another 15-20 minutes over and above the usual reglue, so add that to the bill as a 'tax' on an already-installed bridge plate pickup.

_________________
For the times they are a changin'

- Bob Dylan

Thanks everyone!! I have not seen the guitar yet, the client mailed me a picture of the lifting bridge on his Collings and I’m pretty sure there is a K&K in it. Thought I’d do a preemptive knowledge base query

Great ideas, thanks for the help. I’ll check back with what I did after I see the instrument.

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

Just passing through. Couldn't resist.
Always done it as woodie G describes.

Sent from my Pixel 5a using Tapatalk

Love the caul corral

Geesh look at that! Nice to see you pass through Farmer.

If the bracing in that area is taller than the transducers why not tape a wooden caul spanning the braces inside the guitar and clamp against that? If it is a well fitted bridge and you are using hide glue it shouldn't need bone crushing force to clamp it down.

Not talking about bone crushing force but having the opportunity to add different levels of force to different parts of the bridge. In the repair world (this is said for others Clay not you I know you know this) in the repair world wings are often an issue and occasionally the only thing that really needs any concentrated calming force.

Anyway use vacuum clamping if one wants we think it's less versatile and effective on bridge repairs than using multiple if necessary conventional clamps. We have a lot of tech in our shop, invented some of it too but vacuum clamping was never desired and we don't even have it because other methods for us are preferred.

The last thing you ever want to see is after removing clamps a wing or the middle is still up and not in contact. You can't tell this at the time you do the repair if it's obscured by the membrane. I'll reiterate the dance required with HHG too and the short open time.

Now there is someone who doesn't want to get any on himself Coward!!! Get back here we need ya bro and I hope you are doing great.

By the way we moved a few months ago and have a nice new shop with deer in the front yard, a dog and are appointment only now.

We prefer the cut-out area instead of individual cavities for the transducers and the reason why is transducers are often installed crooked or off center favoring one side or the other. A sloppy caul fits more imperfect transducer installations better. You can see in one of Dave's pics above that one he worked on had transducers off center. This is of course if you want to ever use the caul again and it's not a one-off.

By the way does it matter for a transducer to be off center? I don't think so and I don't think anyone can hear this which would be a favoring of treble or bass to a very slight degree. That's what preamps are for anyway.

Wanted to add that I believe I know some Luthiers who also intentionally install the transducers favoring the perceived weak side of the response so again off center transducers.

2 words: friendly plastic

My understanding / experience has been that the position of the outer transducers matter more than the middle one (or middle ones, the classical model K&K has four) but even the outer aren’t overly sensitive.


Sent from my iPhone using Tapatalk

I don't have a go-bar deck, but if I did, I wonder about cutting a few sticks shorter and then you don't need a caul. I've also seen a classical builder who puts the bridge down, wraps a cord tightly around the lower bout, then uses wedges to apply downward pressure on the bridge. I know many people out there use 315 HHG, but I think John Hall uses 192. I think the one I use is 258(?), so that gives more open time. If your glue joint is accurate, any glue with a small weight on the bridge should work. If I remember, Art Overhauser recommends using no clamps.

In my experience most of the world uses 192 and classical bridges do not have to endure the much higher string tensions of steel strings.

Not using any clamps when regluing a bridge on a steel string would not be recommended at all here.... that is a repair that would fail more than likely. I would not recommend a "rub joint" with no clamps with for new construction on a steel string. We reglue on classicals too and reglues are a bit different than new construction at times because of developed top distortion. We clamp classical bridges too when we reglue them.

Classical bridges do lift too by the way. There is an industry joke what does Cordoba mean in Spanish? Bridge reglue....

We only use 192 but I was under the impression that the higher number/gram strength HHG has LESS open time not more making getting clamps in place even more critical time wise. I'm not sure on less open time for higher gram strength so feel free to correct me if I have it wrong.

Lastly I would not want to glue on a bridge with go bars for a number of reasons. You are distorting the dome on the top with downward pressure unless you brace from inside the box. The level of pressure we would use to glue a bridge might damage a guitar in a go bar deck. Lastly one slip of a go bar and you have a gouge or hole.... on the middle of your top for all to see.

What's wrong with using clamps?

Also once in a while I have to address the notion of no clamps being required to glue on a bridge. Context is everything here because of string tension. So it's important to distinguish if this is a classical bridge or steel string bridge and it's also important to distinguish between new and repair work that makes a difference in the approach too at times.

What Art does if it's a rub joint on a classical is a common practice and likely works fine. It would not work on a steel string if your definition of "work" includes an enduring bond that does not lift.