Official Luthiers Forum!

Hi all.

I've glued my share of classical/flamenco bridges, but I've never really felt safe about my method to hold the bridge in place while the clamps were tight and the glue sets. The results always turned out fine, but the glueing operation was always stressful!

When gluing a steel string bridge, using a Fox type bridge clamp, holding the bridge in place is pretty straight forward. On a classical, there are no holes! I seen Robbie O'Brian use masking tape and simply taping the bridge in place, but that was for a vacum bridge clamp, and it didn't work for me using standard bridge clamps. The bridge had a tendency to move while thightening the clamps.

So I was wondering what method you guys use to hold the bridge in place.

Let me know!

Thanks!

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Alain;
I use the tape to locate system all the time!
It works!

Do NOT use allot of glue-coat only the bridge or top NOT both -no need to if you have a good wood to wood joint.
You can drill 2mm(3mm if using a 3mm saddle) holes at each end of the saddle slot for wooden pins.
Drill these after you have located the position you need.
Then glue that buggar on !
All clamps can pull a piece out of the ideal alignment-so be careful and watch the bridge as you tighten the clamps (for bridge movement)this is really where the tape comes in handy-the distance from the tape to the bridge which should be NOT measurable -should stay that way !
I'm so bad at relating stuff!
Mc

_________________
Mike Collins

Hi Alain
Some people drill 2 holes through the bridge in the saddle slot and into the sounboard. On my first guitar, someone at LMI told me to use round wooden toothpicks with the point cut off, as a dowel. You don't want it to go all the way through the soundboard, and the portion sticking up in the saddle slot can be chiseled off after gluing. In his Hauser online course David Schramm had us make small dowels out of the same wood that the bridge is made of. You cut a small square piece of the wood and then force it through progressively smaller holes that have been drilled through a piece of sheet metal until you get the diameter you want. This way the bridge stays perfectly positioned while gluing.
Wendy

Two thoughts:

Even with pins, if you torque down a clamp, the pins can tear through the softer top and slide sideways. So, mark parts of the perimiter with masking tape jsut to be able to see if it moves.

In a GAL article, one builder explained how to do a rubbed bridge joint with HHG. No clamps are used.

http://www.fileden.com/files/2009/2/11/ ... wedges.jpg

This system, which has been used in Spain for ages, works with a spacer made of plywood that runs from the nut to the saddle. As you push the wedges in the only possible movement is up against this spacer. The spacer has the exact shape of the layout of the strings so you are centering the bridge at the same time! It also includes compensation of course so mark it to remember which side is up. Using HHG and "rubbing" the joint means you really don't need much pressure and the wedges provide enough if your rope is tight. No clamps, no cauls, nothing inside the guitar.

John Ray
Granada

_________________
John Ray
Granada, Spain
blog: http://www.granadaexpert.com/johnray/

I know some don't like it, but I use the tape dam method, from Frets.
It works great for me. I don't put excessive pressure on the bridge, but get good squeeze-out all around. I use HHG and heat the bridge to about 140 or 150* before placing. Clamping takes only moments with everything pre-staged like the first picture.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I just use tape to locate the bridge, but I do use about 5 or more layers so that the bridge sits in a small 'well'. You could use small brads in the saddle slot as insurance but I've never found it necessary. Don't overdo the clamping pressure and it should not move about.

I also make some of my classicals with a tornavoz, so access inside the guitar is not possible, so I'm sometimes limited with my clamping systems, I now use this method on my non-tornavoz guitars as well. The negative rake on the FB, means that clamps on the wood on the FB give sufficient pressure to hold the bridge, the clamps on the wings are just to snug down the wings.



So

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I should have made myself clear, the tape dams are multiple layers of tape cut through on the roll in multiple layers, like Colin's method.

Colin, I like the fingerboard center clamp. Great idea. Saves beating around in the sound hole with those metal rods, and taking a chance on dinging it.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Many ways to do it. i use HHG and finger pressure for 4 or 5 minutes. Believe me, it works.

Thanks to all for the multiple responses!

Lots of good methods I didn't know about.

I think I'll go with the small dowels method. Since the guitar and bridge are finished, it pretty much rules out John's method (although it's a good one to know about!). And since I'd like to wash away the glue squeeze out right after the clamps are set, ity also rules out the tape dams.

The only downside I see to the dowels method is if the bridge has to be taken off eventually; the dowels will be in the way for sure...

Thanks again for your help!

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

Alain;
If a repairman is to remove the bridge hopefully he will remove the saddle first and see the pins.
Then all he has to do is drill them out.
Mike

_________________
Mike Collins

Alain, I assume that you are using HHG for the bridge, which is what I do. I just leave the bridge for five minutes or so for the squeeze out to set and then peel off the tape, 90% of the squeezeout comes away with the tape and the rest is easily removed with whatever is your favourite method. If you are going to use dowels or temporary brads, make sure of your placement as the last thing you want to do is drill a hole through a fan brace.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

Waddy, I can't claim this as my original idea, this was my advice from Joshua when I was making my first tornavoz guitar, it's the way that he does it as there is no access inside of the guitar with the tornavoz in place.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

I knew there was a good reason I used a different colour of wood for those dowels!

_________________
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 just removed a bridge off my #1 to fix some issues. I drilled 2 1/16" holes through the saddle and used toothpicks shaved down to 1/16 as the pins when this was installed. A simple re-drill with a 1/16" drill removed the pins for easy bridge removal.

Thanks Mike. It makes total sens!




I'm using titebond, so I need to lean the glue squeezout while the clamps are in place. And thanks for the heads up for drilling though a brace, but I had thaught of that!

Thanks again for all your help guys!

_________________
Alain Moisan
Former full time builder of Acoustics, Classicals and Flamencos.
(Now building just for fun!)

I like this, Colin!

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

I've never made a classical, but when I made my 2 ukuleles, I used 2 -1/16" drill bits on each end of the saddle slot. I would drill the hole and release the drill from the chuck and just leave it there. Constant pulling in and out will loosen the hole, so you only want to remove the drill bit once to glue. I actually never removed the drill bit from the bridge. You leave both drill bits in the saddle slot and lift the whole bridge keeping the drill bits in the wood.

Mine didn't skate at all once the glue was on. I also didn't drill very deep, just enough to go through the bridge and top, then stop, unchuck the drill bit and leave it there. Then once I got one clamp on, I used pliers to pull the 2 drill bits out, and then finish clamping the wings. Hope that helps.

_________________
Tracy
http://www.luthiersuppliers.com

hi Alain!
I'm not really experienced but I heard a lot about vacuum "clamping". And not only for the bridge, but also for braces. Maybe you could check on this side too!

(Après tout ce que j'ai entendu, vu et déduit de cette technique, j'ai l'impression que la pression est répartie de façon parfaitement égale sur toute la surface de collage, et tu peux même contrôler la pression exacte exercée sur le collage, dépendant de la colle utilisée...)

My 2 cents!

Check LMI, vaccuum pumps are no so expensive.

Francis

_________________
Francis Richer, Montréal
Les Guitares F&M Guitars

I like the clamp/caul setup with the eye-bolts. Do you find the need to use a caul from the underneath as well?

I've had mixed luck with deep throat clamps or bracing with a block from inside and clamping against that. The pin idea looks like the next best thing for me to try.

-Matthew

My inside caul is also part of my hold down system. I just tape it in place before closing the box. It has magnets on the wings to aid in holding it in place after the box is closed. I can put magnets on the outside too, and, hopefully, it will keep the pressure off the tape, and it won't drop in a clunk to the back of the guitar when I'm trying to put the clamps on.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars