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PostPosted: Tue Feb 14, 2017 5:21 am 
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Old Growth Brazilian Rosewood
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I was regluing a bridge yesterday and thought that some of the newer folks here on the forum might enjoy seeing how you can use HHG for bridge gluing (new guitar or a repair) without struggling with the short open time.

This is a Dave Collins idea/innovation by the way and I learned it from him over ten years ago now.

The pics speak for themselves. The dry run is when the bridge is positioned properly and carefully and then two layers of masking tape are applied around it to create a quick placement "well" of sorts. This helps position the bridge when in a hurry and skating on HHG.

Note the fulcrum added to the clamp and where the masking tape supports the clamp in the middle and on the back. The bridge plate caul is already in position in the box. Be sure to use waxed paper or a teflon caul.

These days I preheat my bridges for about 15 seconds in a wimpy 500 watt microwave that is how I warm my lunch too:) The HHG has already been brought to around 145F and has been holding heat there for about 1/2 an hour to be sure that it's ready.

Then I remove the bridge from the dry run, heat it in the microwave, get some paper towels ready both with warm water and dry and some wooden toothpicks available for cleaning up the edges I'm ready to go. If a client comes up now, and they do.... they get told that I'll be right with them and they get to watch me do this...:) They usually find it fascinating.....

The warmed bridge is slapped into position and "snapped" into the masking tape well and the clamp is snugged down. I like plenty of squeeze-out and it's cleaned up with warm water and paper towels. The tape can be removed in about two minutes and that removes much of the excess glue too now in snot-like.... form.

With this method I can apply glue and have the clamp snugged down in easily less than ten seconds.

Hope this helps!


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Last edited by Hesh on Tue Feb 14, 2017 6:29 am, edited 1 time in total.


These users thanked the author Hesh for the post (total 6): drumgerry (Mon Sep 17, 2018 4:45 pm) • DannyV (Tue Apr 18, 2017 9:32 am) • dpetrzelka (Mon Apr 17, 2017 9:24 am) • Pmaj7 (Tue Feb 14, 2017 11:41 am) • Terence Kennedy (Tue Feb 14, 2017 8:59 am) • Clinchriver (Tue Feb 14, 2017 5:51 am)
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PostPosted: Tue Feb 14, 2017 5:43 am 
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Neat, thanks Hesh.
Do you apply the HHG to the bridge, soundboard or both?

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PostPosted: Tue Feb 14, 2017 5:55 am 
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Very nice I just did a new bridge glue up with HHG and I was close. Having the clamp sitting in place is a nice touch.

Colin I apply HHG to the bridge and the soundboard



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PostPosted: Tue Feb 14, 2017 6:12 am 
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I've been using three clamps but pretty much the same thing. Pre-positioning the clamps and adding the masking tape "well" for the bridge help make the process super fast and low stress.

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These users thanked the author SteveSmith for the post: Hesh (Tue Feb 14, 2017 7:21 am)
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PostPosted: Tue Feb 14, 2017 6:35 am 
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Old Growth Brazilian Rosewood
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Colin North wrote:
Neat, thanks Hesh.
Do you apply the HHG to the bridge, soundboard or both?


I just apply to the sound board but I also use a great deal of glue these days. This helps speed things up too.

The bridge is scraped with a single edge razor just before I heat up the bridge in the microwave and the bridge patch is also scraped too.

The only bridges that we have ever had fail, and this really sucked..... were years ago when we were using fish glue and then the instruments later encountered high RH. I know this is controversial since some of you have good luck with Fish but our clients are not always keeping their instruments in the best of environments. Or, in other words, many of our frequent clients are gigging musicians on the road.

Anyway for some years until I saw this method I wanted to try HHG for bridges but did not think that I was fast enough to pull it off before the stuff jelled.

Dave's method made it work for slow poke me here.



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PostPosted: Tue Feb 14, 2017 8:06 am 
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Similar procedure for me when gluing up a bridge, except I use a cam clamp supported by a block of sponge inside the box.

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These users thanked the author Colin North for the post: clint.b (Sun Jul 09, 2017 11:53 pm)
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PostPosted: Tue Feb 14, 2017 9:13 am 
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Brazilian Rosewood
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Gould you just hand hold the bridge in place with HHG and then put clamps on and then heat it up real good as you clamp it?

IOW I am trying to ask basically, could you jsut put glue on the bridge and foot print, almost like sizing it, then jsut put the bridge in place. And say, I don't know, come back the next day and with a heat lamp and some clamps heat the sucker up real good to reactivate the glue and clamp it down?

Or would that severely weaken the joint? I'm not an HHG user but I'm just wondering.


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PostPosted: Tue Feb 14, 2017 9:27 am 
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Koa
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Microwave...brilliant! We've been warming the bridge in foil on the shop's Saltan plate warmer, but the difference between resin bleeds and 'ready-to-glue' is a matter of minutes and judgement. I just adore these sorts of threads - it's always fascinating to see the broad range of solutions for what are routine tasks in our shops!

Given that Mr. North has broadened the topic to include differences from or variations on the author's theme, I have posted a few pictures of of our shop's approach. We have a very similar method of clamp and caul usage, but use an additional Ibex-style clamp to provide a bit more clamping pressure, and add two additional medium-sized cam clamps to remove the shearing and bending loads on the top which are possible if the bridge is set well forward relative to the X-brace intersection and the outer clamp pads are used too aggressively.

Attachment:
RadiusTop bridgeGlueup.jpg


Just as with Messrs. Breakstone and Collin's modified Stewart MacDonald bridge clamp, we dimple for the ball end of the Ibex clamp screw, but have found that for flat-topped bridges such as those that Taylor and Gibson uses, a plywood block with dimples spreads the load more evenly than the stock StewMac caul's cork pads when combined with the outer clamps and cauls. Easing the edges of the cam clamp adjacent to the sound hole allows insertion even after the primary clamps go on, but with some cork sheet to protect the top, all the clamps can go in the sound hole prior to glue-up and rest on the top clear of the bridge patch. We tension the outer clamp pads on the SM caul to the point of seeing squeeze-out, the get the outer cam clamps in place.

Attachment:
FlatTopBridgeGlueup.jpg


On the use of tape for the alignment 'dam' - we were using 3M Delicate Surface tape for the first layer (as seen peeking out from under the standard blue tape mask in the shot), but have gone to StewMac's ultra low tack white paper tape to eliminate the step of heating the last layer of the dam on removal where the surface is degraded, and to cut down on tape residue cleanup...the top layers are still 3-5 layers of standard blue tape.

Attachment:
TapeDamLowTack.jpg


As for the cauls, we use 3/4"/18mm hardwood ply covered with packaging tape, and - after sealing pin, bolt, and pickup holes with some low tack tape, use two small pieces of double-stick to hold it in place until glue-up. Where the outer clamps fall outside the bridge plate caul, we use small rectangular or wedge-shaped 18mm ply blocks covered/held in place just like the main caul. For new construction, we prep the cauls once the bridge plate goes on, to include the supplemental blocks where required, and keep them in the build box. For repair work , we have a couple boxes of cauls that are indexed by brand and model, which avoids having to use small rare earth magnets to lay out a new caul.

Finally - like Messrs. Breakstone & Collins, we are not fans of fish for bridges or other load-bearing work, and use 315g hide for all bridge glue-ups, coating both patch and bridge at glue-up. 6-8 hours is more than enough clamping time for 315g, and the bridge can be loaded as soon as 6 hours with a warm shop. We hang the guitar to minimize any possibility of top distortion while the glue dries, despite any evidence that there is a need for it...we are all deeply irrational creatures, it seems.

Attachment:
BridgeDrying.jpg


Thanks as always, Mr. Breakstone, for the post - it is ever a pleasure to peek inside yours and Mr. Collin's shop!


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Last edited by Woodie G on Tue Feb 14, 2017 10:53 am, edited 1 time in total.


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PostPosted: Tue Feb 14, 2017 10:22 am 
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I scratched my head over this a bit when I first started using HHG, too. Since devising a method of getting my clamping system poised and ready to go, before spreading the glue and placing the bridge, things have gone much more smoothly.

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PostPosted: Tue Feb 14, 2017 10:55 am 
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One of my bench lamps almost always has a heating bulb in it. Either for bridge removal or buying a little more time during glue ups.

Like most luthiers, I have the ever growing box of bridge gluing cauls. I don't mind making them for common bracing designs because I know they will get future use. Making them for brace layouts I'll never see again, or digging through my box looking for one that will work, always gives me that hemorrhaging time/money feeling.
I'm curious, Mr. Hesh how You and others deal with pressure on bridge wings and the endless combinations of bridge plate thicknesses and brace locations.
I can start a different thread if this is a hijack.

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IMG_3015 - Copy.JPG

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IMG_3016 - Copy.JPG

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PostPosted: Tue Feb 14, 2017 2:29 pm 
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I love these threads too. Thanks! I have adopted mot of ideas here.

Looks like David is in the lead with 5 clamps!


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PostPosted: Tue Feb 14, 2017 4:06 pm 
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We use 3/4" hardwood ply for nearly all cauls - either all four clamps rest on the caul (in which case, thickness is the same), or the outer clamps rest on separate small cauls outside the X braces (thickness differences are moot). In either case, there is no shear or bending load on the top because the outer adjustable pads function as just that - adjustable height pads. As long as the bridge plate caul approximates the shape of the bridge plate, and there is room for the small cauls outside the X, there's no need to build a single caul to do both jobs.

The only time we have some real fit issues is when we are working around pickup systems that are not easily removable without damage. K&K and JJB systems take a special caul that usually ends up requiring a little fitting work.

I am cheering for Mr. Farmer...and guessing that he can get at least one more clamp in there! Winner, winner, Chicken dinner!

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PostPosted: Tue Feb 14, 2017 4:16 pm 
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Old Growth Brazilian Rosewood
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Hey David! If you fit the bridge very well to the top, that's what we do, we only glue it on when only slight fingertip pressure is required on the wings to sinch them down.

As such the wing clamps are not doing any heavy lifting and don't have to have any backing at times, not always, but more often than not.

We have cauls too that cover the wings inside the box but we also learned to trial fit, scrape and/or take to the belt sander (know your platen.....) and trial fit again.

When I was building I would floss my bridges on my actual tops and fit them that way. In the repair world time is money and scraping is far faster.

Frank once posted on this forum that he uses the biggest clamp he can fit and clamps that sucker into place. We do that too when need be like for very distorted tops.


Last edited by Hesh on Tue Feb 14, 2017 4:36 pm, edited 1 time in total.

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PostPosted: Tue Feb 14, 2017 4:23 pm 
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I wanted to highlight too in case anyone missed the point. All clamps, cauls, etc are in place and ready to go PRIOR to getting the glue out. I'm not talking about near by, I am saying that everything is in it's exact place. That's the beauty of the method in that once glue is applied to the bridge bottom and/or bridge patch there is no need to reach in the box and position a caul, clamp, etc. Instead all you have to do is twist knobs....

It's so easy even a Hesh can do it....:)



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PostPosted: Tue Feb 14, 2017 4:26 pm 
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Once in a while we have a very distorted top and it's impossible to fit the bridge perfectly before hand. In this case will might add a couple clamps on the wings and use scrap wedges to focus the clamping pressure exactly where we want it. Preheating the bridge extends the open time in this case when we might need it.

Scrap wedges are remarkably useful in the shop.


Last edited by Hesh on Tue Feb 14, 2017 4:41 pm, edited 1 time in total.

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PostPosted: Tue Feb 14, 2017 4:33 pm 
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Another tip that I use at times is when there is runout under the bridge as in one of the pics above I may put a few plastic toothpicks under the "flap" opening it up. When I applied my copious amounts of HHG... I sweep it under the lifted flap, pull the tooth pick and slather more HHG on top of the run out.

Now when I place and clamp my bridge I am also gluing the runout back down in the same operation.

A related discussion is cleaning up the bridge patch, reading runout, scraping vs. sanding, clearing excess finish, rabbiting bridge bottoms and why some don't like clearing finish to the bridge perimeter.

Some of the classical folks use a rub joint and finger pressure but steel string bridges have around twice the tension and I would not recommend this.



These users thanked the author Hesh for the post: Clinchriver (Tue Feb 14, 2017 5:38 pm)
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PostPosted: Tue Feb 14, 2017 6:06 pm 
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Thanks Woodie and Hesh.
I don't use 5 clamps for crushing force. I like the evenness of pressure. No chutes and ladder forces to figure out or guessing how much pressure a cam is applying.

I don't always use that clamp up method but like it. I gives me a good feel for whats going on. It's just a simple pinch between each set of pads and they follow whatever gentle arch is on the bridge.

Most often, I shape the bridge bottom to what nominal arch fits best. I've made small counter forms to all my radius dishes 15',25',40, and 65'. Self stick paper lets me shape the bridge bottom on them. That way very little pressure is needed to bring everything home but I don't try to fit every lump and bump in the top. Just a smooth match of the shape.

After watching Hesh and Dave Collins' video on their site, I now give the bottom a quick scrape just before glue up. Great idea!
I have also used the Ibex/fulcrum/tape method on occasion and can vouch for how well it works.
On some instruments, I can do without the tape by putting a little wedge of wood between a top brace and the clamp inside near the sound hole. That lets me use a clamp on either side for the wings. (and you know how much I like more clamps!)

After a dry run, the clamps are all one finger turn from being tight and resting on my foam spacer. Once I spread glue and put the center clamp on, the joint is warm and not exposed to air so it's relatively leisurely from there.
Multiple clamps are a little more labor intensive to clean squeeze out on the forward edge though.
What I like best is when the braces run right through the center of the wings and i can clamp the brace/wing gently with the outer clamp.


Last edited by david farmer on Tue Feb 14, 2017 6:21 pm, edited 1 time in total.


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PostPosted: Tue Feb 14, 2017 6:18 pm 
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Hesh wrote:
Another tip that I use at times is when there is runout under the bridge as in one of the pics above I may put a few plastic toothpicks under the "flap" opening it up. When I applied my copious amounts of HHG... I sweep it under the lifted flap, pull the tooth pick and slather more HHG on top of the run out.

Now when I place and clamp my bridge I am also gluing the runout back down in the same operation.
.


[:Y:]
Hot hide benefit #6001 is you can glue flaps and top wood transplants down anytime with a soft caul and know you will get perfect adhesion when more glue is added in the bridge glue-up. How ya gonna do that with PVA?



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PostPosted: Tue Feb 14, 2017 8:13 pm 
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This is my setup. I quit using the Stewmac clamp because I was worried about the wing screws taking pressure off the center and getting uneven clamping pressure. A single Ibex clamp seemed to spring a little. Obviously it does work for a lot of folks. I also get all the clamps into position so I can slide them into place and tighten.

Image

My cauls have little extensions for the wing clamps. I usually make a custom caul for repairs and have a small collection now.

Image

I hold the bridge with two 1/16" brads in the saddle slot. Warm it on a heating blanket and heat the top with hair drier.

Really fun to see how everyone does stuff, lots of new ideas.

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PostPosted: Tue Feb 14, 2017 8:29 pm 
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I do it the same way for both new construction and repair, using 2 drills in the outer pin holes, and 3 cam clamps.
I used to use a tape surround like you show, but had some squirm and quit it.

Image

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PostPosted: Tue Feb 14, 2017 8:53 pm 
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From what I understand re: the center-and-wing-clamp approach we use is that - although a well-designed caul for Martin style radiused-top bridges - the Stewmac tool actually reduces glue line pressure at the center of the bridge by the amount of pressure applied by the wing clamps. This could be seen as a net benefit in terms of smoothing out glue line pressure between center and wings, but given the glues we use benefit from a thin, consistent thickness glue line, and the highest stress in the loaded flattop bridge glue line is along the rear of that glue line, we err on the side of caution and go for an approach that assures consistent pressure across the bridge patch.

Mr. Farmer's, Dr. Kennedy's, and Mr. Newton's approaches seem to be similar expressions of that common concern, and a greater number of pressure points can only further even out the pressure seen at the glue line (Mr. Farmer's five clamps still wins...sorry, fellas).

But does it matter, given most joints will be closed to near perfection with just 15-20 psi (the pressure of a single cam clamp spread across the footprint of the bridge patch)? To slightly paraphrase a famous 20th century dictum, 'Extremism in defense of serviceability is no vice.' I am not sure, but certainly for the rectangular Gibson bridges we reglue after doing what flattening we can of the bridge patch, any advantage we can seize seems worth the effort.

While we have you on the thread, Mr. Newton...I finally saw one of your guitars in the shop...an L-00 in for a checkup and some minor set-up work...bravo, Maestro Newton, bravo! A purely lovely little instrument with exactly enough of everything and nothing of excess!

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PostPosted: Tue Feb 14, 2017 11:33 pm 
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I never use or drill bits anymore but in certain situations I use these hollow plastic pins. I stumbled across them at my Ace hardware store. I bet others would find them useful.
The O.D. is .192" which is a strange number but perfect when you slot them with a band saw.The slot makes them roll pins that compress and fit various combinations of holes and tapers while keeping things snug. They are great for bridge plate caps where it's nice to keep the holes small for string ball defense.
The MDF piece in the pic runs against the bandsaw fence and makes slotting them safe. You can make them short and clamp over the top of them. They would drill out easily if they ever got stuck.(mine never have)
These stay play free even after trial fittings because of the spring action.
bevel the ends a bit to get them compressing into a smaller hole.
Attachment:
WIN_20170214_20_11_25_Pro.jpg


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PostPosted: Tue Feb 14, 2017 11:44 pm 
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Cool, do most of you guys just wander around the fasteners section of Ace where all the little boxes are and wait for inspiration? I sure do.

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PostPosted: Wed Feb 15, 2017 7:09 am 
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Just adding a few thoughts - I generally do not like using tape on finished guitars ... YMMV depending on type of finish and age. The beauty of HHG is that it gels and cleanup is easy. I do use the delicate tape method (thanks Woodie) with real tape over top, but for bridge alignment more than cleanup. Cleanup is a cinch with HHG.

Secondly I use 315 gram strength on the bridges ... I've found it makes a difference. More tolerant to any variances in clamp pressure or surface irregularities on repairs. Not all of the guitars that come in for repair at $3-8,000 ... plenty of cheap student guitars come in where routing bridge patches and such are not cost effective. Good line up and 315 allow for these repairs to be cost-effective. I've moved to 315 for all bridges, new construction and otherwise.

Finally ... multiple clamps and multiple independent clamping blocks ... I'm inclined to like that approach ... the integrated Stewmac clamp (and LMI also) are a mixed blessing. Still playing with one vs the other but leaning toward the independent plywood blocks - easy to shape for common profiles.

Andy


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PostPosted: Wed Feb 15, 2017 7:43 am 
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I'm curious for those who are using multiple clamps and 315 gram strength which has a shorter open time IIRC than traditional HHG what your procedure is for gluing on a bridge broken into steps and with approximate times given? I'm also curious what problem 315 gram strength solves that a well glued on bridge with standard strength HHG creates? I'm happy to be a believer if you can justify the value add to the client or Luthier.

Since we fit our bridges well in advance regardless of if it's a cheap instrument or not we don't need a lot of clamping power in so much as I won't glue a bridge on unless it's down everywhere with only slight finger pressure. There are exceptions for highly distorted tops and then we may use two additional clamps with fitted wedges on the wings.

Last year we dropped a producer from our warranty repair list because they wanted us to have a lesser approach to inexpensive instruments and bridge regluing. We couldn't do that because at the end of the day when the thing comes back off it's us who are going to get flamed on the Internet and for peanuts too. As such we plod along doing the whole nine yards in our approach to bridge regluing because.... our name is on it ultimately.

If our SOP (standard operating procedure) for bridge regluing is cost prohibitive for someone truly in need, or good looking...:) we are happy to cave on price but never quality.

With the Stew-Mac bridge gluing caul since we are not snugging things down a great deal, just firmly you can feel and tell when the pressure is lessening in the middle because the wings, which should be snugged down with similar pressure together, a bit here, a bit there, and so on and so forth will continue to turn even past the point of firm contact. You don't want to do that and again it's easy to tell when this is starting to happen.

HHG also draws things together unlike other glues except Fish. We still need clamping pressure for sure but well fitting parts are a huge help here and HHG is also not gap filling also adding to the justification for well fitting parts.

Occasionally we use blocks for certain bridge shapes including my own Heshtone bridges which have a large trailing edge that needs clamping too.

Anyway the beauty of this method that Dave developed and we've used for over a decade now is we can have everything in place in seconds with no drama. This is why I am interested in precisely what others do differently that is also quick enough or relies on reheating or preheating so that HHG jelling is never a possible issue for you.

This thread will have greater value to others if there are multiple methods described in detail is my thinking.

Thanks


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