fractured very tall bridge

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fractured very tall bridge

Postby Mike Ryan » Mon Apr 30, 2018 4:57 pm

I am repairing a curly maple b&s and neck om size guitar with a 3/4" tall bridge, yes 3/4, with a saddle recess less that 1/4 inch deep and it is canted toward the head stock. I needed a very tall very tall saddle in the shallow saddle slot. So, guess what/ the front of the bridge cracked. I think it might be best to just make another tall saddle and route a deeper slot and try to find a very tall saddle bone. What do u guys think? The neck angle is also very very wrong obviously. I could do a neck reset I suppose but this is way way off neck angle wise. It is a bolt on neck.
see photos
Attachments
20180430_134115.jpg
20180430_133954.jpg
Last edited by Mike Ryan on Mon Apr 30, 2018 5:00 pm, edited 1 time in total.
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Re: fractured very tall bridge

Postby Mike Ryan » Mon Apr 30, 2018 4:59 pm

image got rotated when uploaded, sorry.
Attachments
20180430_134115.jpg
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Re: fractured very tall bridge

Postby Mike Ryan » Mon Apr 30, 2018 5:02 pm

This guitar was a one off allegedly build with a guitar builder, It also had a cracked top below the bridge in the seam but I got that to close pretty well with humidification after 2 months in my humidified house in the desert of southern arizona. .
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Re: fractured very tall bridge

Postby Barry Daniels » Tue May 01, 2018 10:03 am

Looks like a lot of the guitars made in Mexico. They normally play them for a couple of years and then throw them away or nail them on the wall of a restaurant.
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Re: fractured very tall bridge

Postby Mike Ryan » Tue May 01, 2018 11:49 am

This one is a very beautiful curly mpl one the guy wants to give to his daughter. My question "is the easiest thing to do here just make another super-thick bridge replacement??? Going to be interesting to heat this bridge enough to get the bridge off. Also find a saddle deep/wide enough to go about 3/8 into the bridge.
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Re: fractured very tall bridge

Postby Freeman Keller » Tue May 01, 2018 11:52 am

Barry Daniels wrote:Looks like a lot of the guitars made in Mexico. They normally play them for a couple of years and then throw them away or nail them on the wall of a restaurant.


Barry, we have a very active Mariachi music program in our local schools. The kids are hard on their instruments, I get to repair them. I think that its kind of interesting that the labels on some of them proudly declare that they are "hand made in China".

Back to the original post, when I saw it my reaction was to get the instrument stabilized and repair any structural damage. Then set the neck geometry based on the top of the bridge, just like always. Then fit a saddle that has at least 2/3 of its total height buried in the bridge, that might mean routing the slot deeper.

The builder must have had a reason for making the bridge the way he did but playable geometry is the same as any other guitar.
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Re: fractured very tall bridge

Postby Freeman Keller » Tue May 01, 2018 11:58 am

Mike Ryan wrote:This one is a very beautiful curly mpl one the guy wants to give to his daughter. My question "is the easiest thing to do here just make another super-thick bridge replacement??? Going to be interesting to heat this bridge enough to get the bridge off. Also find a saddle deep/wide enough to go about 3/8 into the bridge.


The builder made that bridge intentionally - I would duplicate it. I would be very tempted to try routing the slot out deeper and wider, then filling it with rosewood, then route a new slot (like we do on the old martins when the slot needs to be moved or some of those old guitars with the adjustable saddle inserts). As far as the saddle, if it sticks out 1/8 inch it only needs to go into the bridge 1/4, but I would be temped to make it deeper. Just get a taller piece of bone.
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Re: fractured very tall bridge

Postby Alan Carruth » Tue May 01, 2018 1:34 pm

If you don't want to reset the neck, I'd fill the slot and re-rout it so that the saddle tilts backward. This can go a long way toward reducing the tipping force. In fact, if the saddle angle bisects the break angle, there is no tipping force. That's how violins get away with those tall, narrow bridges.

Having the strings so high off the top does put a lot of torque on it, though, and angling the slot back doesn't change that. I'm amazed that top is not more distorted than it looks to be in the photos.
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Re: fractured very tall bridge

Postby Mike Ryan » Tue May 01, 2018 3:30 pm

the front of the saddle slot on the bridge has essentially broken off so I would have to rely on a glued back saddle and saddle and the back of the saddle is really not conducive to clamping forces due to exaggerated slope. I'll see what my friend wants to do.
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Re: fractured very tall bridge

Postby Freeman Keller » Tue May 01, 2018 9:46 pm

It looks like the bridge is laminated from three pieces. Applying heat would worry me that its going to come apart where you don't want it to. Can you plane the top piece off and make a new one? I can't tell what the pin holes would do
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Re: fractured very tall bridge

Postby David King » Wed May 02, 2018 1:57 am

Using something tough like African blackwood to recreate that top layer will minimize the possibility for the leading edge to snap off again. It'd be tempting to remove that curly maple layer in there as well as I can't imagine that it's doing any sonic favors. I usually mill my saddle slots with a 7º back angle to split the break angle a bit closer to 50/50. It can obviously make intonation tricky so I wouldn't go much over 7º. The angle will move the slot forwards so I'd try to add more material in front of the saddle in your new bridge design
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Re: fractured very tall bridge

Postby Todd Stock » Wed May 02, 2018 7:09 am

It there is an option at this point, I'd take a pass on this repair. With that sort of excessive string height over the top and a traditional pinned bridge, nothing good lies in store for that instrument. At some point, the owner may associate your efforts to address the immediate issue with all of the problems that - given the builder's 'choices' with regards to geometry - seem guaranteed to occur.

The trick with these sorts of repairs is to identify them early and make sure the customer understands that the down-stream issues will likely swamp any immediate relief you can provide, then gently guide them out of your shop with best wishes for a speedy resolution. Not cool to refer them on to Guitar Center, either - that is just wrong. Same situation with non-rational customers - try to ID them early and tell them you are booked for the next 3 years...no one needs that sort of crazy.
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Re: fractured very tall bridge

Postby Clay Schaeffer » Thu May 03, 2018 11:33 am

+1 to what Todd said - No good deed goes unpunished.

However..... If it's something you feel you must do and it's a bolt on neck;
I would fit a wedge under the heel to get the neck angle back to a semblance of reality, rout or plane the bridge down to somewhat normal, check the scale length and rerout the saddle slot in the proper spot. (You might also want to place a tag in it written in Hanzi to give yourself some plausible deniability ).
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Re: fractured very tall bridge

Postby Mike Ryan » Thu May 03, 2018 8:47 pm

all interesting ideas. The wedge idea might work. I think I might just make a whole new bridge. What about a neck reset? Too much back angle to correct? This is an undemanding friend of mine and he built this guitar with a "luthier" Man, mistakes include bridge pin holes that are no reamed enough for the ball end to pass easily, this bridge, loose saddle slot. I would have rerouted it but I could see how to stabilize my stew mac plastic saddle slot jig at that height while the bridge is on the body. Amazing break angle at this height. Obviously digging in to the saddle too which had to be very sharp. etc. etc.
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Re: fractured very tall bridge

Postby Clay Schaeffer » Fri May 04, 2018 10:55 am

One thing to check when changing the neck angle is if it will create a "ski jump" of the fretboard extension on the body. If it does you would have to sand and refret the extension or (depending how bad it is) remove the neck and fingerboard completely and add a wedge on the soundboard (a la Humphries) to get a reasonable bridge height.
I use a simple homemade jig to rout saddle slots on bridges that are glued to the soundboard. The white melamine strip helps line up the jig with the saddle location - it has the same offset as the router bit. The square subbase of the router rides in the track formed by the jig. "Start and "Stop" marks are penciled on the jig so the rout is kept in the limits of a drop-in saddle.
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saddle rout jg.jpg
saddle rout jg2.jpg
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Re: fractured very tall bridge

Postby Todd Stock » Sun May 06, 2018 8:00 am

There was a builder that was active in the area for a time and built with faceted sides...likely because he never understood the whole 'heat the wood while moving it' thing. Had one come in a few years ago with terrible bridge geometry, generally awful workmanship, and those crazy asymmetrical polygon sides. Quoted my cost for one of my new instruments and promised to reuse his tuners and bridge pins without up-charge.

Sometimes a guitar is better utilized as a wall hanging.
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Re: fractured very tall bridge

Postby Gordon Bellerose » Sun May 06, 2018 1:11 pm

With a very tall bridge, and a tall saddle also, this would place a very large amount of torque on the top of the guitar.
The leverage created by the height is part of the issue.
Re-routing the saddle does not solve the problem.
After reading what everyone else said I have to agree that as difficult as it may be, a neck re-set is in order.
If it is even possible.

And of course along with that is a new bridge plate, and saddle.
I need your help. I can't possibly make all the mistakes myself!
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Re: fractured very tall bridge

Postby Clay Schaeffer » Sun May 06, 2018 7:38 pm

"Re-routing the saddle does not solve the problem."

If you plane down the existing bridge to a reasonable height then you may also need to re -rout the saddle slot. It would save a little bit of work removing and remaking a bridge.
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Re: fractured very tall bridge

Postby Mike Ryan » Fri May 11, 2018 7:07 pm

Ok, I have the bridge off, fretboard off, cracked in 2 of course at the join with the angled ramp. So new fretboard.
The truss rod was frozen but there was no fillet so I popped it out, was a stewmac looking hot rod and was corroded.
NOW, The neck is a bolt in mortise and tenon and heavily glued in of course. I have never removed a glued in one. Recommendations on how to do that. Light colored glue not hide blue, ff my builds are all just butt joints.
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Re: fractured very tall bridge

Postby Clay Schaeffer » Fri May 11, 2018 10:01 pm

If it is an organic type glue (titebond, elmers, hide glue, etc) vinegar will soften it and allow you to dig it out. Kind of a messy job and best if you use stainless steel or plastic tools to avoid staining - vinegar reacts with mild or carbon steels. Using a small drill bit and drilling in the joint can allow you to get the vinegar in deeper.
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