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I usually don't do repairs through the soundhole, in my restomods I always loosen the bottom to get free-range to repair anything inside. But sometimes I have to do simple repairs for local customers. One standard repair is gluing loose or cracked braces. I got fed up with doing special cauls and messing about without seeing what I do. Especially the hopeless braces deep into the guitar.

So, here is my jig. It works and will put pressure on the brace to be glued with no hassle and no special cauls.

The base for the jig is an air-wedge I bought on amazon. They are made to mount heavy doors and such, but I found a better use for it. The one I bought is 11,5 cm wide and 16,5 cm long, when flat and not inflated with the pump, the bladder is soft and can easily be put through the soundhole. The height of the bladder will be 6 cm inflated.

The jig itself is made of a U shaped aluminum bar, 12 mm wide and 10 mm high. To be able to put pressure on the tip of the slanting brace, I made a little adjustable and movable feet in the end of the bar with a threaded bolt and a nut. A wooden block with a suitable thickness with a cut-out groove matching the width of the aluminum bar is the final part of the jig. A straight piece of aluminum bar can be used to glue the middle of braces, not that common.

The only difficulty with the jig is to adjust the position of the movable feet so that both the bar and the feet are touching the brace at the same time. It has to be test-fitted against the brace shape in the particular guitar. Since all the braces tend to be of the same shape in one guitar (but not the same between makers), the fitting can be done on the most convenient brace closest to the soundhole. I use the holes in the aluminum bar to make sure that the bar itself and the adjustable feet are in contact with the brace. When done, the nut is tightened to secure the position of the adjustable feet and the bar is press fitted to the wooden block as one unit.

The jig is mounted on top of the brace to be glued after the glue is applied. The brace acts like a monorail and the jig can easily and securely be slided to the end of the brace, no matter how deep into the guitar the brace is.

The bladder will apply a big force to both the jig/brace and the opposite top or bottom. Around 200 kg according to the advertising. It is very important that that force is counteracted with two pieces of scrap wood across the guitar with two or three clamps from the outside. If not, the guitar will probably explode! With the air wedge, you don't need to make a special caul for the opposite side, the soft bladder will shape itself to any brace on the opposite top/bottom when inflated.

With clamps on the outside and the jig in place, the only thing left is to push the air wedge through the soundhole and place it over the wooden block in the jig. Then pump away. I pumped until the safety valve on the pump blew out as an experiment, adding probably 200 kg to the top of the brace. No problems at all with clamps on the outside. You should probably use less force than that.

When the glue is dry, the bladder is easily emptied with a valve on the pump, and you have a very nice glued brace.

The jig really shines with braces deep into the guitar. Depending on the height of the sides, wooden cauls with different thicknesses can easily be made from scrap wood.

Gluing braces through the soundhole will be more fun for me in the future

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Thanks Roger. I employ a similar technique using the SM scissor jacks and their flexible extension arms. Your cauls look nicely engineered.

I have one of these, but it can't be used on small parlor guitars - that's what I'm working with almost all the time. My version will apply more force and have no problems with braces on the opposite side of the brace to be glued coming in the way of the jack.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Great idea Roger. I use the SM scissor jack as well, but I’m keeping a note of the idea for those thinner bodies!


Pierre
Guitares Torvisse

_________________
Pierre Castonguay

We use numerous small jigs made out of non-stick material, teflon etc that our glues won't stick to with high power rare earth magnets and I don't speak of any of the ones I see here ours have at least 42 lbs of pull per square inch. They are so strong you can really hurt yourself with these if they jump and you didn't do the planning correctly.

Very easy to use they are too.

I'm off all week and not in the city but if someone reminds me I will takes some pics. I recently posted our big-arse "Big Bertha" here that we use when powerful clamping and flattening is required. One of Dave's innovations we considered productizing so many people who saw it made it or wanted to buy one. We call it the "brace mouse" in that it looks like a computer mouse only it's arse end has a rare earth magnet counter sunk in it.

I did a bit of product development today. I put a bevel on the wooden block to be able to see the glue squeeze out and how tight the glue joint is.

Super magnets may be a great way to do the same thing, but with my jig there is no danger of crushing fingers

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

But with your jig you need a hardware store of sharp metal things poking around inside and outside a shiny new instrument that has yet.... yet to be scratched....

We can see our squeeze out perfectly and there is no risk of us gluing the magnetic clamping caul to the guitar.

No thanks Roger I greatly prefer what we use and do.

But with your jig you need a hardware store of sharp metal things poking around inside and outside a shiny new instrument that has yet.... yet to be scratched.... I can see at least seven tooling elements to what you came up with in your first picture. We use one and a spare magnet.

We can see our squeeze out perfectly and there is no risk of us gluing the magnetic clamping caul to the guitar.

With magnets we can set our clamps in an area that we can reach and then slide them into place from the outside of the instrument..... For anyone who does repair work this is huge....

Regarding injury or damage to an instrument we've clamped hundreds and hundreds of instruments for over a decade with rare earth magnets and never injured ourselves or an instrument. I've been on this forum a very long time, Roger and it is my way to point out even if there is a remote chance of someone injuring themselves with anything related to what I post. So I mention it as often as I can out of an abundance of caution and get this... a sincere and genuine caring and like for many if not most of of my forum fellow participants. Please don't use my completeness in having concern for others possibly being injured as your opportunity to proclaim that what you do is superior.

No thanks Roger I greatly prefer what we use and do.

The problem with sharp metal in my jig is not existing, I would be more worried about super magnets doing their thing. When did I ever say my method was superior? There's more than one way to skin a cat.

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

You said with your way there is no risk of crushing fingers.....

Regarding sharp metal dull metal to a guitar is potentially damaging if you jab it, scrape it, set the instrument on it and it was on your bench and you didn't see it. Because of the potential hazards of these magnets we prep the patient, remove near by metal, make sure we are not wearing pace makers and then move the magnets into place. Works great.

Went into work today even though we are closed all week for vacations and took some pics of some of our rare earth magnet jigs that we much prefer over alternatives. Our jigs have been used for over a decade on countless instruments.

For those who may not have ever seen a very high volume repair shop I took some pics too. We don't and won't sell a thing, want a pack of strings I may give it to you but I won't sell it and there is a long story behind this for another time.

We are currently repairing over 1,100 guitars only annually and that does not count mandos, banjos and bases. Bring us something else and you get to see the front door twice in only a few seconds. We do not work on what we are not expert with. Our minimum service is about $100 and a full set-up. With this said when I say we repair over 1,100 guitars only annually these are not twisting a truss rod with your 55 piece Craftsman socket set these are generally very comprehensive and often complex repairs. We won't change strings or replace a broken string and we learned long ago that to make the economics of a repair only Lutherie shop work you have to be highly selective in what you take in...... an understatement.

Pictured are three of our rare earth magnet jigs, there are others not pictured.

The small one with a notch in it the notch is to register on the crown of a brace. The set screw adjusts the magnet(s) depth for brace height and the third magnet goes on the outside of the instrument with a protective caul/shield. The "Collin's Brace Mouse" as I named it rocks on the curved part and is adjustable for any brace we have ever encountered.

The pull on these magnets is 42 lbs per square inch and very strong. You will not be able to pull them apart without twisting and tilting them and once you learn how to do this it's easy but does bother my hernias these days.

The one with the crank is "Big Bertha" and superb for flattening large areas. It has a matching glue resistant piece that is not shown.

The little two magnet side by side jig also does cracks nicely forcing things nice and level as the glue cures.

I don't remember what Dave made the housings out of and he's Nanook of the North this week and out of range up with the Grizzles refreshing his courage for the next Ov*tion that comes our way. He was using teflon though so this may be that.

Anyway sure lots of ways to do things and this is how we have produced over $2M in repair only revenue from our shop in the last nearly ten years. Again we don't sell a thing all our revenue is from our labor fixing guitars and such. It's not academic for us, it's not fodder for forum discussion and exchanging notes - it's our reality. Our jigs are not intended to be clever or cool they are intended to make us money and provide our clients with real value and a safe place to have superb work done.

Rare earth magnets have been a game changer for us, we've never damaged an instrument with them although the potential exists but it exists with every tool you have by the way.

Back to the brace mouse which is the reason for my posts in this thread attempting to offer a point of view that was not represented here.

From the earliest days of Lutherie mini go-bars were often used to reglue a brace. A short stick with a notch on one end that was wedged against something solid inside the box and then the notch rides on the brace crown. Works great and if you don't have a suitable firm location of the top of the stick a flat caul taped in place works great and takes less than a minute to do. I think that these "sticks" with notches in them for regluing braces are shown in Teeter's well respected early repair book. So there is another way a third way. Jacks too a forth way.

I do love the stick though it does not get simpler than that and you need nothing to make it work but a dang stick and something to cut it with.

Yep lots of ways to do these things and I always prefer less complex, less costly and methods that have less potential to damage an instrument.

To be clear too the last brace mouse pic with a magnet under it that's the outside the box magnet stuck to it for storage, see the non-stick divider?

I came up with these fulcrum style, Neodymium magnet clamps, which have been very versatile for various loose brace scenarios. 1/8" X 7/8" discs, double stick taped to an 1/8 bit of plywood with a triangular stick glued to it. The magnets to be used are carefully set up on the bench in an alternating order, polarities reversed to oppose it's neighbor, before anything goes in the sound hole. Do this with the topside magnets as well. Pinching and or flying hazard if the work is not done methodically! You can see my image, the spacing can be quite close. Clear your work area of anything ferrous, another precaution to avoid unexpected magnetic attractions, except where you want it. I place them by hand, again, methodically. I don't have to spend much time doing a dry clamp first (always recommended) and changes just involve putting the magnets in different locations, usually goes pretty fast.

Nice Paul looks great and I'm sure it works great too. We can place our's about the same distance that you are using with no interference as well.

Wanted to mention that our love affair with rare earth magnets got off to a slow start. The first batch we ordered was shipped but never arrived. We thought they may be stuck to the side of a metal mail box. So the supplier resent more and they made it.

Over a year later the original shipment showed up with a very beat up box....

Hesh, this looks like HDPE. I use it all the time to make cauls after someone here suggested it a few years ago. Impervious to any glue, easy to work with.


Pierre
Guitares Torvisse

_________________
Pierre Castonguay

Thanks Pierre my friend I think you're right!

>You said with your way there is no risk of crushing fingers.....

Yes, and that's the truth. That "big bertha" should be able to do that, it's surely a big and powerful one!

Anyway. We all use the method that we know and trust. My air wedge is perfect for me, and I'm glad I don't have to handle super magnets more than I do. I use them to level both sides of a side/top or bottom when gluing cracks. They always take me by surprise at least once every time

_________________
New will change the old,
turn to ashes or gold

http://www.gammelgura.se

Tell ya what I do and it's very simple. I make 'go bars' that fit snug inside the guitar from the brace that needs to be reglued to the opposite side. I number them so that they fit in order to take up the arch of the top or back and use a thin spatula to get glue under the brace then fit the go bars in and clamp from the outside using protective cauls.

Works for me.

I like the the lever magnet setup though that's neat. And Roger it looks like a clever solution you found there too.