Official Luthiers Forum!

Hi everyone, I’ve been lurking around here for several months, but this is my first time posting. You’ve got a great community of very talented people here, and the fact that everyone seems so willing to share is inspiring! I don’t build guitars, but I have done some complete (solidbody) refrets and fingerboard replacements, made nuts etc. I've repaired a few minor cracks, and done many setups, electronic jobs and fret dresses on my own guitars and those of friends.

Anyway, a cracked headstock on an inexpensive Chinese guitar of mine is about to provide me with some more repair experience. Due to the nature of the crack, I have a few questions and am wondering what the best method of approaching the repair is.

The crack starts at the nut below the fingerboard, and runs about 3” or so down each side of the neck.



The shonky plastic factory nut popped off easily, but the crack had already taken the small piece in the middle of the nut shelf above the truss rod. I saved the chipped piece. If I pull the headstock back to open the crack, it only wants to open up about 1 - 1.5mm, or .040” - .060” before it feels like I’m risking splitting it further.

What glue would you use for this situation, and what's the most effective way to get it in there? Do I just try and get as much Titebond in there with a feeler gauge as I can, trying to avoid the truss rod? Or wick some thin CA as far down as I can first?

Any advice is greatly appreciated!

If the crack closes well, work some thinned TB glue in as far as you can, without getting too much in the truss rod cavity, followed by as much full strength as possible, and clamp it for a day. String tension works in your favour with this type of break.

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

+1

You may.... need to relevel and dress the frets after all is said and done too depending on how well it comes out.

Another way to get glue into the deep recesses of the thing is compressed air. As always avoiding getting glue near the rod is a good idea too.

Was this a knock off a stand accident?

And - welcome to the OLF!

Thanks guys! How much can titebond be thinned?

Hesh - I don't have an air compressor, but I may try and borrow one off someone. I assume gentle pressure would be sufficient?

The frets are badly in need of work anyway, so a level and dress is already on the to do list. The damage was done in shipping.

A few drops of Titebond, a drop or two of water - mix, apply, repeat.
Hold the joint open with a tool, or a toothpick - work in the glue from both from the edge, clamp.
Gravity is your friend, and thinned glue will wick into the crack - just keep flexing it.
Touch up the finish. You are a hero.

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"Act your age, not your shoe size" - Prince

Sure gentle air pressure and gravity as Chris suggested should do the trick nicely.

When we thin Titebond I'm sure that we weaken it a bit but depending on the application that may not be a problem. This application where as mentioned string tension is on your side should not be a problem.

Thinned Titebond can and does help the full strength stuff migrate into the repair as well. For crack repairs I often "size" the joint with clean fingers pushing 1/2 strength Ttitebond into the crack and that "wetting" attracts the full strength stuff that I follow up with. Same principals apply here.

I believe our resident former Titebond engineer advised that thinning to 50% viscosity (about 10% by volume) has only negligible effects on strength.

Found the original info.

"One other point I forgot to mention: If you are planning to use PVA such as Titebond Original or Extend, I always recommend diluting it with a 5% to 10% addition of water which will result in 50% and 75% decreases in viscosity without changing final bond strength. Wetting both bonding surfaces with water and a small brush and allowing it to soak in for a few minutes is also not a bad idea. My reasons for these changes are that adding water to the interface will slow down the drying process of the adhesive ever so slightly and provide additional open and closed assembly time. The diluted adhesive will further extend assembly time and allow you to ensure the fit is absolutely perfect before really torquing down the clamps. Since the adhesive is significantly thinner it will get into all of the little nooks and crannies commonly found in a headstock break, and will then proceed to squeeze out more readily than undiluted adhesive. Not only does this have the cosmetic advantage of forming a super-thin glueline: thin gluelines are also much stronger than thicker ones. "

That was posted by forum member hugh.evans, complete text can be found here http://luthiersforum.com/forum/viewtopic.php?f=10122&t=37863&p=549213&hilit=thin+titebond#p549213

There is always the syringe thing if you can find a needle that will let you push the thinned Titebond through it. Also, stand it up while you are working on it. May as well let gravity help too.

I thought about trying a syringe, but rather than spending $/time experimenting to find the appropriate needle gauge from a chemist, or waiting for a dedicated glue syringe to arrive, I just went and did it with what I had on hand.

With the guitar on a stand, I propped the crack open with a toothpick on each side, and pushed the thinned glue in the sides with a small brush. I remembered I had an aerosol can of "compressed air" here already, and gently using that definitely helped to get it in there. Soon afterward I started pondering what the actual contents of that can was and realised those things aren't compressed air at all, but some other compressed gas. It doesn't say exactly what it is on this particular can, other than "highly flammable". I must Google it later.

Anyway, full strength glue went in the easier to reach places, then I clamped it up using a couple of cauls that I made from bondo/bog/body filler. I got nice squeeze out much further down the crack than I had expected. Hopefully the truss rod didn't cop much.

It has been clamped up for the last 12 hours, and I will leave it for another 12 before I touch it!

Maybe I'm overly cautious, but I always leave mine in the clamps for 48 hours.

Next time you need a syringe for gluing.... try the local veterinarian supply.
You can get big ones!

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"Act your age, not your shoe size" - Prince

My wife works at a vet clinic, so that's where I get mine from. Syringes work great for measuring 2 part finishing epoxy as well.
I found that putting a Postit sticker on her dashboard gets them to me quicker!

Alex

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"Indecision is the key to flexibility" .... Bumper sticker

Opening and closing the joint will sort of pump and suck the glue in further too.

Dilution, compressed air, pumping the joint, etc. You have got good advice everybody has covered this well but for the future I feel compelled to caution against using a feeler gauge or anything inside a break like that or other splits where there are rough fibers. You could easily displace some wood fibers/slivers so that the surfaces don't mate well and you will never have either as strong or as cosmetic a repair. Compressed air unless gentle can displace fibers as well. I prefer using a vacuum to compressed air. Ones finger with dilution and pumping the joint is the best I think with a fibrous rough joint.
L.

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Cut to size.....Beat to fit.....Paint to match.

Blowing through a soda straw seems to give about the right amount of pressure to get the glue into the joint. Plus it allows you to use both hands on the joint while blowing. Any moisture in your breath doesn't harm the glue strength.

Ed