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Some super clean work in David's photos there, very cool! David also shows how some very talented Luthiers can be wrapped a bit too tight at times... if you notice the grain orientation of his pin hole plugs.... What a sick mind..... I love it - this is my world too!

Well of course you have to align the grain!

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Steve Smith
"Music is what feelings sound like"

Those photos are some I just dug up. maybe not the best example because there was so much going on with that instrument. someone had previously routed the deep rectangular hole. I have a few more that will show the idea better.
I would only plug the holes if there is a need to, (moving the location, holes way too big, etc.). Your pics look like the plate is in good shape.
This patch was maybe .025" thick. You can see the soft rubber glued it all the way down into every hollow. Then when it is leveled, the edges feather to nothing and the hollows are filled. You get a level surface without removing any more original spruce.
The keys to the method I think are the right combination of squishy and hard cauls, and Hot hide glue.

Thank you very much David, the photos are very helpful. I am working on this one right now and the holes are good so not having to plug them will save me a lot of time.

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Steve Smith
"Music is what feelings sound like"

Started work on the bridge by filling a couple of divots. I've done this before and I just use a gouge to shape the defect then use the same gouge to make a matching plug. I used CA for these.

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Steve Smith
"Music is what feelings sound like"

I used the drum sander to make an 0.020" spruce patch. I made a couple in this shot because the first one blew up in the sander


Glued the patch to the bridge footprint with HHG per David's instructions

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Steve Smith
"Music is what feelings sound like"

On to the back crack. I used a modified X-Acto blade to size the crack for a 0.020" mahogany splint.

I just used a pallet knife so the brace wouldn't get glued with the splint. The jack was there so I could use a clamp to align the sides of the crack.

The two piece splint was glued in with HHG and then leveled. I'll address the finish issues when I finish all the other repair tasks.

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Steve Smith
"Music is what feelings sound like"

Your rolling Steve.
I love my Stew Mac scissor jacks!
I hope your sailing stays smooth.

Back to the bridge. Got it cleaned up and ready to go. Definitely a chisel and scraper job. It's surprising how well this method fills in even small defects. Thanks David!

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Steve Smith
"Music is what feelings sound like"

Nice job Steve!
Puts spruce fibers right where you want them.
I find a bonus is the Hide glue saturates the shim so the surface is already sized for putting on the bridge.
Here's what happens when people keep re-gluing a bridge without addressing the hollow.

I suppose that would be a good way to lose a reglued bridge in a hurry.

I wonder if hide glue's property of drawing parts tighter together helps pull the fibers into the defects better than if you used Titebond or some other glue.

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Steve Smith
"Music is what feelings sound like"

Could be. I think the supposed "drawing together" feature of hide glue is just another way of saying it shrinks quite a bit as it dries.
With thin spruce, the moisture in any glue softens it and a squishy pad lays it down in the hollows.

There are two important aspects to Hide glue in this type of repair. One is, because the patches feather to nothing at a low angle, the glue line is wide and hide glue sticks to it's self full strength.
The other is reversibility. The guitar in the photo above is a 38' D-18. the rule is remove no more wood. I'm guessing a bridge has been on and off that one at least 4 times in it's life. Some of those removals were brutal. With a tool submarining deeply against the grain. If it comes off again down the road, remnants of a patch can be gently moistened, carefully removed, and a new patch applied. With an AR glue, another layer of glue saturated wood has to be removed.

David, again, thanks for sharing this technique, it works great.

I've only used hide glue for bridges and the more I learn, the happier I am that I've done so.

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Steve Smith
"Music is what feelings sound like"

That hollow is where they hide their dope.... Tommy Chong who I got to meet and speak with for an entire evening once says "If you like cavity searches cross an international border with a guitar case...."

In addition to David's excellent reply about the value of HHG here some of us assign that magical, mystical qualities that we can't prove as to how HHG dries so very hard and crystalline that we think it to be unsurpassed in terms of glue for vibrational transfer. Again, no proof here, just a strong belief.

The pulling parts together thing should not be mistaken for clamping ability beyond what a rub joint provides. As it dries it shrinks and pulls itself and what ever it's sticking to together but not with anything to speak of in terms of clamping force per square inch mind you. HHG also benefits from perfect, wood-to-wood joints prepared with care.

When it's appropriate for the instrument to save time and money such as regluing a bridge on a torn-up Ov*tion where a decent joint is not economically feasible in terms of repair budget HHG is not a good choice and instead something with gap filling qualities is a good way to go. If you are thinking ep*xy that's that I'm thinking too but certainly not for this cool little guitar.

Taking into account how poorly the bridge patches are typically prepared on many f*ctory instruments it's a wonder they can keep a bridge on at all....

Got the bridge glued on.

Located with a double layer of tape.

I use tape to hold the bridge caul in place. A bit of a pain but haven't seen a better way yet.


Got everything ready. Tape holds the clamps in place. Saw somebody else do that and it works great. Heat lamp keeps everything warm. I just got this heat lamp and it sure beats trying to use an old hair dryer.


All glued up. Got a little sloppy with the glue bottle on the front edge. I would have liked another clamp so guess I'll order one.

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Steve Smith
"Music is what feelings sound like"

Looking good Steve.
The heat lamp is the bomb. I never touch my hair dryer Any more.
If your getting more Stew Mac clamps, the shorter ones are easier to manage if you don't need the length.
Is that high adhesion tape? The green tape I have could winch a car out of a ditch if you stuck it to the hood.

Nicely done Steve! In our set-up class we show folks how to set-up a dry run for HHG and tape all clamps in place using a masking tape well for bridge location just like you are doing. Folks can have the clamps set and down in 10 seconds or less. This is the method that made HHG my first choice for bridges because it takes the drama out of the process.

I stick the bridge in our microwave (600 watts, little guy) for 12 seconds and that keeps it pretty hot for several minutes too.

David and Hesh, thank you both.

David, the tape is 3M 233 which is high tack. It's what I usually use although I keep the lower-tack blue painters tape around too.

Hesh, this is the one that I plan to bring to Ann Arbor in April. I'm really looking forward to the classes.

_________________
Steve Smith
"Music is what feelings sound like"

Nice, that spruce filler is the ticket

It is a great technique and I could see it being useful in other places such as under the fretboard extension.

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Steve Smith
"Music is what feelings sound like"

Bridge came out fine. This shot shows the two sides where I have some minor finish repair to do. The other two sides came out perfect.

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Steve Smith
"Music is what feelings sound like"

Cool Steve and you are doing some really great work there!

If this is the one that you want to fret in class when you come I might want to talk you though board leveling in advance of your arrival here since we will have to compression fret this one (no truss rod, etc.). Compression fretting is really no more difficult but it can take a little longer to do because we check progress under actual string tension a number of times throughout the process. That tells us where we want more or less forward bow, etc. to actually string the beast up and tune to pitch.

Not a problem though I just want you to be finished when everyone else is. One of the benefits of having both Dave and I working with ya is that either one of us can spend more time with you for this one AND we are very happy to do so too! Cool guitar too!

Hesh, this is the one that's coming to class. I need to glue one brace and cleat the crack then I'll be ready to reset the neck. I'll be happy to have you talk me through the reset and board leveling so that we will have time to fret this little gem.

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Steve Smith
"Music is what feelings sound like"

Been a bit slow on this one due to a trip out west and another guitar I need to work on. But did clean out the holes and installed a nice set of unslotted bone pins.

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Steve Smith
"Music is what feelings sound like"

Finally got the other guitar project under control so I'm back on this one. I used thinned Tightbond to glue the loose back brace. The StewMac jack works great and allowed me to easily clamp this one from the outside. Squeeze out was cleaned up after the photo. Next I'll put in a couple of cleats and this crack that has been bugging me go 40+ years will be a thing of the past.

_________________
Steve Smith
"Music is what feelings sound like"