Broken neck on Gibson Jam Master.

[Michael Lewis]

String Dude, Where in northern CA are you?

[mirwa]

So now I'm wondering what kind of glue would be best to inject in to the crack before I clamp it up for the best results

I agree with John, the original neck fit up by manufacturer may have been a little lapse, let's call it a Friday instrument.

Best course is to clean and yes hide glue it, of course you could always fit splines (basically a biscuit joint) and have it permanently done and stronger, titebond will work as well, but you would possibly always see some form of flexing happening at that point.

As far as done a few, yep"........., we average at least one a week for last 20 yrs, so that's roughly 1000 broken necks repaired

Steve

[Bernie Daniel]

I agree with John, the original neck fit up by manufacturer may have been a little lapse, let's call it a Friday instrument.

Best course is to clean and yes hide glue it, of course you could always fit splines (basically a biscuit joint) and have it permanently done and stronger, titebond will work as well, but you would possibly always see some form of flexing happening at that point.

As far as done a few, yep"........., we average at least one a week for last 20 yrs, so that's roughly 1000 broken necks repaired

Steve

Steve that is a failed joint between the old neck wood and under lay that I put on about 4 - 5 year ago to repair a neck break.

That specifically answers the question that John raise too --i.e., it is not a fresh break.

I am thinking of cleaning it out old glue with a strand of wet yarn or maybe cotton string? I would have tried to clean it before but was worried that water might weaken the glue farther up in the break and case the separation area to grow?

[Bernie Daniel]

Again not trying to steal this thread but this is more on mandolin neck repairs and maybe this post will give the OP some ideas on what could be done?

I've been thinking about the failed repair that I pictured in #22 of this thread. Here is a diagram of that issue.

Since cleaning out the crack (red dashed line) will be hard and problematic and the gluing surface is not ideal anyway, maybe I could just cut it out and insert a new piece of maple over it?

I could stain the inserted maple a dark red-brown so it would not be an eye sore.

Diagram below is probably self-explanatory



Or one could go this way? But probably diagram #1 is the best?

[sunburst]

Your diagrams both show end grain butt joints: not good.
I'm not convinced of the wisdom of the graft approach, but something like this would be better because there is no real end grain joint. The fit would need to be very good (chalk fit) for the repair to be viable.

[Bernie Daniel]

Your diagrams both show end grain butt joints: not good.
I'm not convinced of the wisdom of the graft approach, but something like this would be better because there is no real end grain joint. The fit would need to be very good (chalk fit) for the repair to be viable.

Thanks for the input. So short of a new neck would any approach be better than a graft?

[sunburst]

I don't know.
A lot depends on the presence, depth and size of a truss rod and truss rod pocket. Grafting on a whole new peghead, or grafting on the existing peghead with the damaged wood removed and replaced with new wood, sort of like a double graft would probably be a good repair. Some wood pieced in between the neck shaft and peghead, that is. It would require removing the truss rod, doing the repair, then re-cutting the slot and replacing the truss rod.
I might decide to just glue the opening that's there and hope for the best.

[Jeff Mando]

I might decide to just glue the opening that's there and hope for the best.

That's what I was thinking. It might hold.

[Bernie Daniel]

I don't know.
A lot depends on the presence, depth and size of a truss rod and truss rod pocket. Grafting on a whole new peghead, or grafting on the existing peghead with the damaged wood removed and replaced with new wood, sort of like a double graft would probably be a good repair. Some wood pieced in between the neck shaft and peghead, that is. It would require removing the truss rod, doing the repair, then re-cutting the slot and replacing the truss rod.
I might decide to just glue the opening that's there and hope for the best.

OK, Thanks! I think I'll try that first -- after all what have I got to lose?

I don't have any hide glue crystals right now but I'll just buy a few packets of Knox unflavored gelatin at Krogers tomorrow.

One recipe I have is 35 mls of water and one packet of gelatin.

I'll heat the glue to 140 degrees F and then use a syringe and needle to irrigate the inside surfaces on the neck opening two or three times -- i.e., use the hot glue solution to flush out the dirt and old glue.

Then I'll squirt in another syringe of fresh clean glue and clamp it.

I should be able to fit of the caul and clamp up in about than 15 seconds.

Then we'll see what happens!

Note to OP in case you did not know it Knox gelatin is essentially very pure and expensive hide glue! Might come in handy to glue up your neck too!

[Wes Brandt]

Is fish glue that common for instrument making? I have heard very little about it.

[mirwa]

Cleanliness is the most important thing when regluing a surface, steam works great, alcohol is good too.

Johns graft is better because you eliminate an end grain join, personally I do niot feel the need for a complete back plate or graft, two splines out of a wood like maple are super strong

This is a photo of one of the 335's we did this week,

It had cracked twice, so we always fit splines when a headstock comes in and has been previously repaired by someone

- First photo, the cracked head just above its already repaired crack which was also around the manufacturers join.
- Second photo, splines fitted initial air brushing to colour the splines and initial crack line
- Third photo full cover coat of colour and re-assembled

Steve

[mirwa]

Now this is probably one of the worst we had to repair, still looking for a finished photo

The point, anything can be repaired, with very little evidence of having ever existed

Steve

[Bernie Daniel]

Is fish glue that common for instrument making? I have heard very little about it.

Maybe not so common but used just the same? There is information on Roger Siminoff's web page about it.

[darylcrisp]

i think Taylor guitar company is using some sort of fish glue on some models now-will do more research and if I find out exacts i'll post here again.

d

[Tom Haywood]

The OP's description sounds like a broken headstock, but I guess it could be a joint separation between the headstock and neck. Photos are absolutely necessary to get any good advice, but a headstock repair or joint repair is the likely solution rather than a neck replacement. Much cheaper and likely much stronger than the original. Good advice already given on who to call. Posting photos here is easy but not intuitive. Here's how it works on my PCs. When you choose "insert image" while in the reply box you will get a dialogue box that looks like you are ready to simply choose your photo and post it, but there's more to do. First, select the button at the bottom that says "Browse", then choose the tab at the top that says "Computer", find your image file on the computer and click it. The name of that file will now appear in the dialogue box. Click the "Upload" button and wait a minute or so while it uploads. When it finishes there will be a path/file name showing in the reply box on the cafe. Click "Post Reply" to submit it and the photo will magically appear with your post. Complicated to figure out but easy once you get it.

[Bernie Daniel]

OK, Thanks! I think I'll try that first -- after all what have I got to lose?

I don't have any hide glue crystals right now but I'll just buy a few packets of Knox unflavored gelatin at Krogers tomorrow.

One recipe I have is 35 mls of water and one packet of gelatin.

I'll heat the glue to 140 degrees F and then use a syringe and needle to irrigate the inside surfaces on the neck opening two or three times -- i.e., use the hot glue solution to flush out the dirt and old glue.

Then I'll squirt in another syringe of fresh clean glue and clamp it.

I should be able to fit of the caul and clamp up in about than 15 seconds.

Then we'll see what happens!

Note to OP in case you did not know it Knox gelatin is essentially very pure and expensive hide glue! Might come in handy to glue up your neck too!

Is it true that you can use hot hide glue to bond two damp or wet wood surfaces? I assume it must be OK because the glue is water-based but many things I assume about glues are often not true!

[skygazer]

Now this is probably one of the worst we had to repair, still looking for a finished photo

The point, anything can be repaired, with very little evidence of having ever existed

Steve

Maybe I've worked on fiberglass boats too much. But when I look at that horrible break, I can't see why you would use hide glue. Not like you ever need to separate it again to work on the guitar.

I would use a high quality marine epoxy, totally weather proof and seemingly permanent. I can't think of a single instance where something (including loads of wood) that I epoxied fell apart or broke again in that spot.

Nice clean shatter should go right back together.

If there is some good reason to use hide glue please explain it to the uninitiated ignorant sailors among us. Thanks!

[skygazer]

It had cracked twice, so we always fit splines when a headstock comes in and has been previously repaired by someoneSteve

I really like the splines, super strong!

[sunburst]

Sailors and boat builders are "always" wondering why luthiers don't use epoxy. They've used epoxy for boats "forever', it works, it's strong, it's waterproof... why don't we luthiers see the light, come to our senses and use epoxy? As craftsmen, we sometimes have a tendency to want to apply our preferred methods and materials to tasks that we are not as familiar with as our usual work.

The biggest advantage of epoxy, especially in boat building is; it's waterproof. We don't need waterproof in instruments, except in cases of occasional accidents. Suffice it to say, we don't normally have to plan for immersion in water when we choose materials for instruments. Another advantage of epoxy is it's gap-filling properties. When we can't get a good glue joint because parts don't fit well, we can still get them to stick together if we use epoxy. Joining dissimilar materials is another use for epoxy. For example, wood and carbon fiber.
Hot hide glue resists tensile failure about as well as epoxy, it forms a much thinner glue line so it is less visible in a joint or in a repair, it resists dry heat better than epoxy, something that shouldn't matter; we shouldn't have to plan for excessive heat any more than for immersion in water, but many of the same people who would never put their mandolin in the swimming pool will leave it in the hot car in the summer.
As long as we have a good joint or a good fit between broken parts in an instrument repair, we get a joint plenty strong using hot hide glue. We get a thin, often invisible glue line that doesn't show badly under dyes and finishes, we get high heat resistance, and when the part breaks again, we have a glue that we can clean off and/or work with when doing subsequent repairs.
There are situations where epoxy is a good choice in luthierie, dissimilar materials, gaps, end grain joints, that sort of thing, but when the wooden parts fit and a good side grain glue joint can be made, hide glue has the advantage in most cases.

Frankly, the broken headstock in Mirwa's picture doesn't look that bad to me. The wood is split along the grain, and as long as good alignment and fit can be accomplished, I would have good confidence in a hide glue repair. When the neck wood is fractured across the grain, that is when splines and possibly epoxy can come into play. Whatever broke that thing, that could happen again, and if it does, repairing it a second time will be an easier job if there is hide glue in there rather than epoxy.
For me, the decision to use epoxy in a broken neck repair is the last choice before a full replacement of the neck. In other words, the neck is so badly broken that it is a judgement call whether to repair or replace it, and sometimes vintage originality can be a part of that decision. If the neck gets broken again, it will probably be time for a replacement, so the CF splines and epoxy that I've used in fractured necks will probably not be a problem for the next repairer, who will probably be replacing the neck.

[skygazer]

Sailors and boat builders are "always" wondering why luthiers don't use epoxy....Hot hide glue resists tensile failure about as well as epoxy, it forms a much thinner glue line so it is less visible in a joint or in a repair...

Thank you John for that excellent and detailed answer and explanation.!!

Very enlightening.

After I posted I did consider that the epoxy line would always show unless you were to paint over it. Forget staining, no chance.

And I hadn't even thought about vintage instruments.

I do only consider epoxy when I'm sure that it will never need to come apart again. Otherwise I use a glue.

Personally, I also get things wet so waterproof is good. My first handmade guitar spent almost it's entire outdoors, often behind my bed in a tipi, sometimes on a boat or in the boathouse, even @ 20° below zero F. Guess it was well made, still fine! I'm extremely careful about thermal shock, easier to avoid than occasional wet.

My "new" vintage '20's mandolin has camped out every night in an open tarp since I got it, and it's rained every night. I purchased it in a thunderstorm. Maybe it's a rainmaker.

[mirwa]

Frankly, the broken headstock in Mirwa's picture doesn't look that bad to me. The wood is split along the grain, and as long as good alignment and fit can be accomplished, I would have good confidence in a hide glue repair.

I totally agree.

If the customer had a first time crack and that was the crack, I would glue it and send it on its way.

But

If a neck has cracked before I always recommend putting a set of splines in it as an option. On that neck the customer took our advice and went the splines, I even guarantee that those splines will never ever break, that is how confident I am of the strength imparted to the headstock area.

Steve

[mirwa]

This one came in on friday, we have not touched it.

The guy bought it new in japan in a store and then flew back to australia, when he got it out of its case he found it cracked, next time he went back to japan, he had it repaired, lets agree the repair is a bit average looking, he has then flown back to australia only to find again its broken

I offered to him the simple glue and clamp but recommended it get splined, he has taken the spline option as well, so this will be done on monday, I guarantee him it will never crack again,

I think when we repair headstocks, you have to give some consideration to its use or abuse, if its been repaired once and broken again, then its likely to keep happening, be that due to its design, use, abuse, or the handling of it from others. So preventative measures are sometimes a good option, all of course IMO

Steve

[darylcrisp]

This one came in on friday, we have not touched it.

The guy bought it new in japan in a store and then flew back to australia, when he got it out of its case he found it cracked, next time he went back to japan, he had it repaired, lets agree the repair is a bit average looking, he has then flown back to australia only to find again its broken

I offered to him the simple glue and clamp but recommended it get splined, he has taken the spline option as well, so this will be done on monday, I guarantee him it will never crack again,

I think when we repair headstocks, you have to give some consideration to its use or abuse, if its been repaired once and broken again, then its likely to keep happening, be that due to its design, use, abuse, or the handling of it from others. So preventative measures are sometimes a good option, all of course IMO

Steve

Steve
please post a picture when it has been repaired.
thanks
d

[Scott L]

If you are in Northern CA, you should give Michael Lewis a call. He is someone who knows mandolins and is a master builder. He also does repair and restoration work...NFI.

[Vernon Hughes]

Here's a testament to hide glue..My dad set his brand new kala uke bass behind the car to load up for a gig,forgot something,ran into the house and forgot to load it. Backed right over it packed in the gig bag. The first pic is how it came to me, the second is after reglueing and in the drop filling lacquer phase and the other two are after finishing up and restringing. It's holding up just fine with no splines.Just glued the major pieces back together first and added the smaller splinters after that.What a puzzle it was.