Official Luthiers Forum!

I got out my no1, 000 (15yrs old) the other day. I hadn't played it for over a year and I can get my fingernail under the bridge
for about a 16th or more along the tail side length of it. Do I have to remove it clean and reglue or can I just put some epoxy or other glue under it?

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Mike McNerney

Best to remove it.

Sent from my SM-G950U1 using Tapatalk

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John

If it was -my guitar- and I originally used hide glue to attach the bridge, I would work some hot hide glue under the back of the bridge and clamp it back down, knowing that if it failed I could remove and reglue it, and only inconvenience myself.
I have reglued loose veneers this way without problems, but admittedly it is a less stressed joint.

I'd be using feeler gauges to probe the extent of the separation before I did anything else. If I didn't already have a bunch of sets (gearhead days) of feeler gauges, they're cheap.

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Peter Havriluk

Remove it and epoxy is not a proper glue for a bridge I would use Titebond Original or HHG.

A lifting bridge is a tell tale of the instrument being dried out and this is the time of year in your region that this happens. Did the case have augmented humidity control or your home?

The proper repair for us is full removal, clean up the surfaces, scrape the bridge to fit the top with minimal finger pressure and then HHG with all clamps in place in under 15 seconds. Titebond Original is OK too but we always use HHG. I would not recommend HHG unless you are comfortable with it and can meet it's small open time requirements with the clamps.

remove it. Then check the bottom of the bridge to see if it had a good glue joint.
NOT convex or concave. from front to rear. End to end!
Make sure you all the finish was removed!
then reglue. Glue choice is yours .You'll get many suggestions.

End to end is dependent on arch of the top.

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Mike Collins

That's the right way to do it

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Steve Smith
"Music is what feelings sound like"

OK, removal it is.

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Mike McNerney

Good choice. Here's what we do:

1). Remove bridge, carefully reading top runout to inform us of pallet knife insertion direction. If this does not make sense please ask I am happy to elaborate.

2). Clean up bridge patch cutting back any finish under the bridge to very close to but not into the bridge perimeter. I stay about .010" inside the bridge perimeter these days.

3). Clean up bridge bottom.

4). Trial fit bridge and we want it to sit in the exact position with only minimal finger tip pressure on the wings to keep it down everywhere.

5). Once it sits nicely in place we do a dry run clamping it in place and we want the wings and the middle clamped. So spend some time figuring out how you and your clamps and cauls will do this. You need a caul inside the box too higher than the X-brace intersection.

6). Once you have it clamped nicely in place as a dry run use masking tape and make a masking tape "well" around the two wings and the leading edge so you have a horse stall of sorts to slap the bridge into when the glue is deployed and time and is short.

7). Remove all but the tape, scrape the bridge bottom with a single edge razor 15 minutes or less before applying glue of choice, use Titebond original or HHG and then glue it up in accordance with the requirements of the glue you use.

8). Once the clamps are in place and snugged remove the masking tape well, clean up squeeze out with warm water, paper towel and I like a wooden tooth pick.

Pat yourself on the back for a job well done.

I leave clamps in place depending on the glue overnight. You can remove them with HHG in only 4 hours and we've done it in even less time but I would just go 24 hours for both glues. Do remove the clamps after 24 hours though. Important point is no string tension for 24 hours.

I don't think I saw this mentioned anywhere - - - index the bridge BEFORE REMOVING IT, so it'll go back to whence it came after all the scraping and fitting is done. I've used a 1/16" drill bit, there's thin nails at the hardware store that are a nice interference fit. I drill a hole at either end of the saddle slot through the bridge, soundboard, and bridge plate and the bridge can be located back to its original position. It helps align things when gluing, too.

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Peter Havriluk

For alignment, I use 1/2" long brads in each end of the saddle slot. The gauge is such that a #56 drill (0.0465") is a perfect size pilot hole.
I also use those brads for aligning/gluing fingerboards, peghead veneers, and tops and backs.
Drilling those pilot holes before removing a bridge or fingerboard certainly simplifies the reglue.
Rub soap or wax on the brads to allow for removal after the glue sets.

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John

We properly locate the bridge in the clamping dry run. This is a repair not new construction so there will be an impression of the bridge in the finish to inform where it was.

So in the dry run we use masking tape, two layers on three sides to make that "horse stall" that I mentioned. The idea is HHG will be used and time is short so we need it to self locate quickly in the well we created with tape. Or, in other words I can slather on the HHG and slap that puppy down quickly with no worries that it's improperly located. The masking tape well prevents the bridge from sliding around as well.

When the tape is removed maybe a minute or so after the clamps are snugged the tape removes most of the squeeze-out in one operation except for that 4th side of the bridge that was not taped.

Now much of the time we also rabbit the bridge bottom and clear finish to very close to the perimeter of the bridge foot print. This creates a "pocket" that the bridge will also snap into.

I don't mention the rabbeting here much anymore since so few have the jig to do this it really doesn't help anyone to mention something you can't do...

So with the masking tape well and the rabbiting of the bridge bottom we have two mechanisms that the bridge snaps into and self locates, quickly while the HHG clock is ticking.

Our goal is to take anything out of play that sucks time once the HHG is deployed.

It works very well for us.

OK Hesh how do I determine the runout.
And on some new construction I am getting close to fitting the bridges and I need a tutrorial on how to match the curve to the top.
I watched Parkers but of course it is for an archtop and he hollows out the bridge.

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Mike McNerney

Mike, if you read through the other thread going on about Master Grade Tops it leads to a fine explanation of how to determine which way the grain is running…

Hi Mike, hope you are doing great and Happy New year to you.

For reading runout: First we read runout when regluing a bridge for the bridge removal process. We are going to use pallet knives and such, thin, flat, metal tools with rounded edges to get under the bridge and release the remaining glue bond from the top.

So the goal here is to insert the tools in a direction that helps to lay top wood fibers back down not get under them and lift them and damage the top. This is why we want to read runout when removing a bridge. It's rarely mentioned (here) but a key part of doing-no-harm, quality repair work. The better the condition of the top when the bridge is off the less work has to be done to the mating gluing surface when we reglue the bridge.

So if you've ever looked straight on at a guitar and one side was darker than the other with a clear line down the middle what you are seeing is how the light in the room refracts differently because of the top run out. This is very much like when you mow your lawn and go one way for a row and the other way for the next row. The light refracts differently for the two rows when viewed because the grass is leaning in opposite directions because of how the mower cut it.

I tip the guitar up at the head stock as if to look at the neck straightness and view the top. The lighter color side has the runout going toward the tail end of the instrument or away from me.

This is just me but the next thing I do is take a piece of masking tape, tape it to my shirt, remove it (this is to make it less tacky) and then stick it on my clean bench. Next I take a marker and make a large arrow on it. I place the tape (when the marker is sure to be dry...) on the side of the guitar with the runout running one way or the other with the arrow corresponding to the direction of the runout. This step is optional but I do it because it informs me which direction to insert the pallet knives to loosen the bridge. With this determined I do at it using what I've learned to help me get the bridge off cleanly with less or no top damage.

Removal is a heat process we use tightly fitting cardboard shields lined in foil with the shiny side facing out. I use HVAC reflective tape to span any gaps that might expose the guitar top and finish to the heat I am going to apply.

Now we do this professionally so our methods not only work great they work fast but you have to be vigilant and present in the moment the entire time to avoid a fire or damage.

We use a heat lamp after the shields are in place to heat up the bridge that is poking through the cardboard lined in foil shield. I heat for maybe a minute with the lamp moving left and right over the bridge and very nearly touching it or just 1/2" an inch away.

We've always used heat lamps including for neck removal of the extension. A few years ago one of the big producers of guitars took our advice and now uses heat lamps too for extension removal and such. You just have to be present in the moment because of the fire risk.

With BRW bridges you will see some smoke at times and the oils start to run and smell them too. So I heat for maybe a minute and then place the heat lamp safely somewhere where it will not catch anything on fire and turn it off. With the pallet knives I then insert being informed as to the direction by having read and marked the top for runout.

If you used a Titebond original like glue or HHG I am looking for the feel in the knives to be gooey and softer as the glue starts to soften. If the glue does not feel soft or I hear or feel cracking I replace the shield and heat some more until things feel soft.

When the glue is soft I carefully and slowly make progress with the knives going slowly not wanting to damage the top. At some point the bridge pops off.

The the fun of expanding the bridge patch, cleaning up the surfaces, scraping the bridge bottom to better fit the top begins.

Be sure before you start any of this to understand why the bridge lifted so this does not happen again. There are two primary reasons whey a bridge will lift.

1). The guitar dried out

2). Internal damage or structure failure such as a loose brace permitting the guitar top to seek a different shape or radius.

If any of these things or conditions exist fix them first before removing and replacing the bridge.

Hope this helps it's a comprehensive approach to a professional bridge reglue and evaluation of anything related.

We spend the extra time doing all of this and as such our reglues show zero tell tale that the bridge ever lifted. We do not clear finish to the peremeter because that can look both sloppy and not OEMish AND it takes choices away from the next luthier who has to reattach the bridge if the steward lets the thing dry out again. We remove finish very close to the perimeter but not all the way to it.

Mike let me know if you have any questions?

Thanks

That’s exactly what I do as well.

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