Official Luthiers Forum!

Whatever you do, don't eat the bridge! or the top for that matter.

Adding a platen to your vacuum press, if you don't already have one, is always a useful piece of equipment. As far as gluing the bridge with 315 HHG goes, it could definitely help if you are having problems with open assembly time. It might push your luck a bit, and the wrong combination of heat and rapid assembly could starve the joint... Not the most likely scenario but you are on your way to setting up the conditions to make it happen. I would recommend running some experiments with it. Set up a bunch of spruce scraps and either a spare bridge or block or ebony/rosewood that is the right size and shape. Try different temperatures and clamp times. As long as the end result shreds the spruce when pulled off, you have an effectively perfect result. As a starting point, set the platen to perhaps 160°F and possibly even mist the bonding surface with water just before attaching the bridge. Glue up, pull vacuum, and after a few minutes switch off the platen and allow the whole assembly to cool to room temperature.

It's been done before, but hide glue will always involve some trial and error. Once you have the process nailed down it's hard to beat.

Filippo, I use fish glue with a vacuum fixture on the bridge and it is so simple. What advantage would you get with hide glue over fish glue? I admire your work, so I'm sure you have a reason, but I don't know what it would be,
thanks Mike

Why 315? Have you had problems with slower HHG? No advice. I already have enough trouble getting regular HHG on fast enough.

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Mike Lindstrom

Get in touch with OLF member and Wissenborn expert Tony Francis, IIRC he likes to use high gram strength hide glue for certain tasks and probably has some advice for you.

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Rian Gitar og Mandolin

It's probably down to another issue rather than the fault of the 192G Hide Glue.
I've only ever had one bridge failure with using that strength of HHG and even that wasn't the fault of the glue but the fit of the bridge, the bridge also happened to be Ebony which tends to move an enormous amount when you hit it with water based glues.
I can honestly say that I haven't used any clamps on a bridge for near on 10 years, just light finger pressure for around 4 minutes. I do size the bridge though (especially Ebony), let dry and refit. I always apply glue to both surfaces, position the bridge, pull it off and apply more glue.

What makes you suspect the glue? Why not jump to 250 strength?
Wow, cool! Cl or SS?
You are getting it wet, drying, and re sanding the radius in the bottom of the bridge?
3 layers of glue? Sounds like a lot. What's the idea there?

HHG doesn't layer. The new hot glue melts the old glue when the bridge is re-placed on the top, and rubbed into position and held.

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

I get that Waddy. But, I'm just thinking; you already spread glue on both pieces, then, after you put them together, you pull them apart just to put more glue in? Sounds a bit excessive, but that's why I asked him what the point was.
( sorry Filippo for getting off the point)

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Pat

I only size the bridges with Ebony because it moves so much. Try it, the main body might be fine but the wings will almost certainly curl. My bridges are thin so even the main body moves.
The application and reapplication of glue is (I guess) designed to size both surfaces and prevent a starved joint. That's how I was taught to do it using finger pressure only method. It's worked, stood the test of time and is hardly time consuming. No real need to change anything.

I read in GAL that one of the strongest glue joints is a rubbed hide glue joint. For a bridge, after applying glue, put the bridge in place and rub it back and forth along the long direction until you feel it start to grab, then position it where you want it and do not clamp. This requires that the bridge and top are properly shaped to fit together without clamp pressure. I haven't tried it. I suppose one should practice on scraps first.

Filippo,
I've glued a myriad of different bridge woods to Cedar, Spruce, and Redwood. I have never had a problem with regular hide glue and I often use fairly oily Rosewoods like Bois de Rose. I have always used vacuum clamping and my prep work is flawless. My opinion is that there is something wrong with either your prep work or process that is giving you trouble. Too many folks use regular hide glue and never have any problems. Or is there something particularly unusual about what you are gluing or trying to accomplish that may be an issue. You are welcome to call me at 386.690.2567 if you want to discuss in more detail.

It's not really a rubbed joint that I do although I might move the bridge a little to squeeze excess glue out. I don't rub it until it locks though. I apply just enough finger pressure, for 4 minutes.
I use tape damns to locate. Two in front, one at a wing. That gives you two open sides to rub as much as you want.

Me either. I've tried a few braces, and I am kind of liking it. But, once it grabs, it's really difficult to move! And with a bridge, it's all about getting it in the exact right spot.

And Michael, you don't rub it until it locks? I don't get it...

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Pat

This isn't rocket science. I apply glue to the bridge. I apply glue to the soundboard. I press bridge in position. I remove and repeat the glue. I position bridge and apply finger pressure for 4 minutes. That's it. The glue is thin enough that I get squeeze out, although not watery thin. I didn't come up with this technique. I got it from David Van Edwards Lute making course. It's a repairers technique, saves them having to remove the soundboard. It obviously works very well because the footprint of a Lute bridge is pretty small, yet it can carry 25 strings each pulling around 2.5 - 3 Kg's each. Total is around 60Kg's on a bridge that is half the footprint of a SS Bridge.
The technique will not work on soundboards that flex a lot. On a fan braced Classical I have to use a prop just underneath the bridge area.
The tape is for positioning. Two tabs on the front end of the bridge (actually on the soundboard), one tab positioned just to the left (or right) of a wing. As I stated in my previous reply - that leaves two sides of the bridge open i.e. not enclosed by the tape. Therefore you can do a rubbed joint, if you want to.

I fully agree with Simon: This isn't rocket surgery. Part of the beauty of HHG is that you can get away with hand pressure for clamping force and end up with a perfect joint. Prep and execution are the most likely culprits, and that's not your fault, it's just part of the constant process of learning.

Fillipo,

I'll weigh in here, but with only limited experience--this is from my challenge build #3. This is a BRW bridge (dyed black to match the ebony fb), I used 315gm glue and a rubbed joint. I didn't preheat anything, just a swipe of glue on the top, a swipe on the bottom of the bridge, and I set it. I drilled two locating pin holes through the E string holes in the bridge, and gently "rubbed" the joint until I felt it getting sticky. I stuck in the locating pins and let it set for a few minutes. I then removed the pins before the glue hardened and I could easily get them out. It's been under string tension for two months with no movement so far..... JMHO.