Removing Acoustic bridge and refitting. Photo Essay.

[muttley600]

I agreed to do a short photo essay for another site that detailed the pulling of an acoustic bridge and re-gluing it along with the fitting of a new saddle. I've decided to post it here as well in response to this thread for any and all that may find it of interest.

The reason for the rather drastic operation is that the bridge has started to lift on the bass wing after the top was subjected to a severe impact of some sort. The case suffered the greatest damage. A good advertisement for a decent case for your axe. They are cheaper than a new guitar and in this instance has saved a lot of further expensive repair work.

There are several ways to remove a bridge. I always like to try and do it cold first but on occasion a bit of heat to the area is required to soften the glue line. As this is a guitar I built some fifteen years ago I'm certain the original was put on with Titebond Original. I've only ever used hide glue or Titebond Original for bridges and a quick check of my notes from back then proves it.

I can get the parting knife under the wing of the bridge of the bass side and that makes a good place to start. I start by masking off the surrounding area and see how far I can separate the join without pulling any of the top away with it. This needs to be done slowly and carefully. working with the direction of the grain and without moisture. A lot of people advise using water to help, it doesn't all it does is damage the top by making it easier to pull the grain up with the bridge.

Progress stalled a bit at this point as the glue was holding on pretty good around the centre. A little localised heat should sort that. I use a sheet of polystyrene to mask off the surrounding area and use a combination of an angle poise lamp and a domestic iron to get some heat into the bridge. Not too much but just enough to get the parting knife to start moving through the glue line again.

(There's an image missing here because I can't get it to show I'll edit and upload it when I'm in front of my machine with photo editing software)

I've got the edge up all the way round now taking care not to lift any of the top with it or damage the bridge and I can get a larger parting knife in there. The one I'm using is a cake Icing tool that I've ground to a fine edge and polished to give a sharp flat edge. Nearly there now and particular care is need when the bridge is nearly free. That last little bit can just pop off and take spruce with it so real care on the last bit and voilà the bridge is off.

This one has come off reasonably cleanly and the next task is to clean up the top and the bottom of the bridge. Done with scrapers and a little careful sanding with very fine grit paper. Now I'll turn to getting the bridge back on.

Obviously the bridge wants to go back in exactly the same place. The bridge pin holes provide a method of locating the bridge and a simple tool I made up years ago provides the clamping pressure.

The base plate above is of a shape that allows it to sit on the bridge plate inside the guitar while the bolts come up through the two outside bridge pin hole. The bridge can then be dropped on top and clamped down with another shaped plate as below.

The main clamping pressure comes from the two big brass threaded knobs that bolt onto the threads placed through the bridge. The wings of the bridge are helped down using two bolts threaded through the edge of the clamp. This is all done dry (without glue) to check alignment and make sure a good joint is possible. Once I'm happy with it. I'll take is apart and glue up.

Glued up and cleaned up. It's time to set it aside for twenty four hours to give the glue time to fully cure.

 

[muttley600]

Just a few followup notes.

This is the most common way of removing a bridge. I don't recommend it to the feint of heart. The other popular method involves a large mallet and a 2" wide chisel. You don't want the details trust me but it works if you know what your doing. It's known as "popping the bridge" and I first saw it done by an old time repairer. He taught me how and I can't bring myself to do it that way even now.

 

[Zaphod B]

My firewall is blocking the pics so I'll check them out later from home. The text is very informative, Muttley - great post.

Now about the "bridge popping"......

 

[muttley600]

My firewall is blocking the pics so I'll check them out later from home. The text is very informative, Muttley - great post.

Now about the "bridge popping"......

You go round the join with a 2" chisel tapping it gently to score the lacquer/glue join. Then with the chisel held at a short angle you give it one maybe two hefty blows with all your strength.

Yes it does work but it takes a lot of nerve. It's never taken me longer than an hour to get a bridge off so I don't do it that way. It also only works with certain glue lines so you have to be sure you know what it has been put on with.

 

[danw]

Thanks for info -- this is definitely relevant to a renovation I'm about to attempt on a junk guitar I just bought. A followup question: Suppose I refinish the top. When I put the bridge back on, I assume I'll want it to sit on a bridge-shaped unfinished section. Would it be better to mask that area off and not finish it, or just finish all over and scrape it back off in one section? Does it matter?

 

[muttley600]

Thanks for info -- this is definitely relevant to a renovation I'm about to attempt on a junk guitar I just bought. A followup question: Suppose I refinish the top. When I put the bridge back on, I assume I'll want it to sit on a bridge-shaped unfinished section. Would it be better to mask that area off and not finish it, or just finish all over and scrape it back off in one section? Does it matter?

These days I mask off and then remove after finishing. Either way will work. I use veneer tape because it's thin as a cigarette paper and gummed on one side. Once the lacquer has dried but not cured I then knife the outline, scrap away most of the lacquer and a very light application of a damp cloth will remove the veneer tape leaving a good clean surface for the bridge to go on. I prefer it this way because you get no finish left in the grain.

What finish are you going to be using?

 

[Fusioninspace]

Thanks for posting that. That was very cool. It's not something I would personally try in the near future - but it's a great overview of the process. I really liked your home made clamp - it looks extremely simple, yet extremely effective.

Good pics also.

 

[muttley600]

Thanks for posting that. That was very cool. It's not something I would personally try in the near future - but it's a great overview of the process. I really liked your home made clamp - it looks extremely simple, yet extremely effective.

Good pics also.

I have the Sloane bridge clamp and variations on it but for this job where the bridge pin holes are already reamed the caul clamp pictured is better. I only use the Sloan on pinless bridges now. The Caul idea is not original although I do claim to have been using mine longer than Dave Collins in one form or another. In truth most luthiery tools are just adaptations of others and we all make our own to suit our methods.

 

[Milnoque]

Thanks for the thread Muttley.

FWIW I used to use a couple of bricklayers margin trowels that I ground to suit my needs to lift bridges. The offset handle made the job much easier. The better ones have very thin stiff blades and work quite well.

 

[muttley600]

Thanks for the thread Muttley.

FWIW I used to use a couple of bricklayers margin trowels that I ground to suit my needs to lift bridges. The offset handle made the job much easier. The better ones have very thin stiff blades and work quite well.

There you go you see, I like a nice flexible palette knife type thingy, gives me more control and I want it as thin as possible too. I have similar but wouldn't use it for this job. the essential thing is that whatever you use it has a fine polished edge and a taper on the part that starts the parting.

 

[danw]

I prefer it this way because you get no finish left in the grain.

What finish are you going to be using?

Thanks. That makes sense about not wanting finish down in the grain; I hadn't thought of that. I don't have any spray equipment, so it'll have to be something I can brush on. I finished my last project with shellac followed by Tru-oil, and I'm pretty happy with the result, but I'm open to suggestion, too.

 

[muttley600]

Thanks. That makes sense about not wanting finish down in the grain; I hadn't thought of that. I don't have any spray equipment, so it'll have to be something I can brush on. I finished my last project with shellac followed by Tru-oil, and I'm pretty happy with the result, but I'm open to suggestion, too.

That's a good finish for a top and underrated in my opinion. It's relatively easy to do and as easy as any hand applied finish. You say you've done it before so I wont detail any methods other than to say when you sand back go right through the grits to 2000 and take your time. With a finish like that the better the prep the better the finished result, although that holds true for any finish.

For a harder more durable and glossier finish applied by hand I would recommend KTM water borne lacquer as discussed in Whitestrats recent thread. Any specific questions just ask.

 

[stevieb]

Thanks. That makes sense about not wanting finish down in the grain; I hadn't thought of that. I don't have any spray equipment, so it'll have to be something I can brush on. I finished my last project with shellac followed by Tru-oil, and I'm pretty happy with the result, but I'm open to suggestion, too.

A Prevail Sprayer works well with NCL. Available at any hardware or home improvement store.

 

[danw]

Thanks for the rec. I had heard the term before, but I never looked it up until just now. Those do look useful. But for now, I've heard enough negative things about nitro that I'm content to stay away from it.

 

[Light]

Just a few followup notes.

This is the most common way of removing a bridge. I don't recommend it to the feint of heart. The other popular method involves a large mallet and a 2" wide chisel. You don't want the details trust me but it works if you know what your doing. It's known as "popping the bridge" and I first saw it done by an old time repairer. He taught me how and I can't bring myself to do it that way even now.

Pussy!


That's the only way I've ever removed a bridge, and the only way we do it with any guitar which is not too delicate to take the blows (in which case, the bridge is usually already falling off on it's own). No big blow at the end though, just a bunch of gentle taps until it pops. Our experience is that it takes much less top wood along with it than any other method. Well, except for those old Harmony's and such where they never removed the finish under the bridge. Those usually come off really cleanly!


I like the brass knobs on your call. We mostly use some very deep throat C-clamps, though when I've built acoustics I've always used a vacuum clamping setup.

Oh yeah, and if you need to use heat for removing a bridge, I HIGHLY recommend getting the LMI heating blankets. I've never used them on a bridge, but I have for bridge plates, fingerboards, etc. (not to mention bending molds), and they truly are the Bee's Knees. Not as good for side bending as our old Overholtzer forms (we've got both the classical and the Drednaught - one of the real advantages to having been in business for almost 40 years!), but better than anything else I've seen people use (LIGHTBULBS? Really? Not enough heat).


Light

"Cowards can never be moral."
M.K. Gandhi

 

[muttley600]

Pussy!


That's the only way I've ever removed a bridge, and the only way we do it with any guitar which is not too delicate to take the blows (in which case, the bridge is usually already falling off on it's own). No big blow at the end though, just a bunch of gentle taps until it pops. Our experience is that it takes much less top wood along with it than any other method. Well, except for those old Harmony's and such where they never removed the finish under the bridge. Those usually come off really cleanly!


I like the brass knobs on your call. We mostly use some very deep throat C-clamps, though when I've built acoustics I've always used a vacuum clamping setup.


Light

"Cowards can never be moral."
M.K. Gandhi

Ha, pussy eh,,

I guess a lot of it has to do with what your brought up with. Coming from a background of early stuff where hide was the norm and parting was always done with a little heat and a knife I've stuck with it. I rarely have any breakout that way. I have done the popping the bridge thing but not that often.

The caul knobs are just a couple of hardwarestore door knobs I had kicking about. You now how us guys hate to chuck anything and use whatever comes to hand. They do work well though.

 

[Light]

The caul knobs are just a couple of hardwarestore door knobs I had kicking about. You now how us guys hate to chuck anything and use whatever comes to hand. They do work well though.

Oh God, you should see the back shelves of our shop - the mess is unbelievable. The thing I don't understand, though, is why we always have every single screw on the planet, except for the one I need.



Light

"Cowards can never be moral."
M.K. Gandhi

 

[muttley600]

Oh God, you should see the back shelves of our shop - the mess is unbelievable. The thing I don't understand, though, is why we always have every single screw on the planet, except for the one I need.



Light

"Cowards can never be moral."
M.K. Gandhi

That's because I have a box full of them but don't need them.

But I bet you have the ones I'm looking for right now.

 

[antichef]

Pussy!


That's the only way I've ever removed a bridge, and the only way we do it with any guitar which is not too delicate to take the blows (in which case, the bridge is usually already falling off on it's own). No big blow at the end though, just a bunch of gentle taps until it pops. Our experience is that it takes much less top wood along with it than any other method. Well, except for those old Harmony's and such where they never removed the finish under the bridge. Those usually come off really cleanly!

Hey, I'm using the search function, OK? - Don't mean to resurrect another thread (not that this one has passed away or ever should, imo), but last night I decided to finally throw away a Fender 12 string acoustic whose neck had broken for the third time (this is one I decided to attempt repair on myself, btw ) - before it went in the heap, I decided to pull off whatever I could -- I aggressively went after the bridge with a mallet and a piece of 1x4 pushed up against it. Snap! [clinkle...] a sliver of bridge came loose and fell to the floor. The rest of the bridge remained with the body as it left the building...

At least I'm not a pussy (or wasn't up until then, anyway)

 

[Light]

Hey, I'm using the search function, OK? - Don't mean to resurrect another thread (not that this one has passed away or ever should, imo), but last night I decided to finally throw away a Fender 12 string acoustic whose neck had broken for the third time (this is one I decided to attempt repair on myself, btw ) - before it went in the heap, I decided to pull off whatever I could -- I aggressively went after the bridge with a mallet and a piece of 1x4 pushed up against it. Snap! [clinkle...] a sliver of bridge came loose and fell to the floor. The rest of the bridge remained with the body as it left the building...

At least I'm not a pussy (or wasn't up until then, anyway)

You don't have to shock the bridge, you have to shock the glue joint. That's why you use a chisel, not a block of wood.


Light

"Cowards can never be moral."
M.K. Gandhi