So in this instructable I will show you how to repair a severe neck break. If you have any questions about the repair feel free to leave a comment.
Also if you love this repair you can vote for it or one of the other amazing repairs in the Fix it! contest
Step 1: Tools + Materials
This is what I used:
1 x g clamp x 300mm - you can use other clamps but avoid quick clamps if possible as the offer significantly less pressure
Bandsaw -(a jig saw or even a coping saw would work in place)
Titebond III glue
Mallet - my one I use for this has a plastic cap which is helpful but not nessecarily required
Allen key - Whatever size fits your guitar
A small scrap piece of wood
A small piece of rubber or leather
Note on Glues: most modern adhesives will do the trick, titebond II or III is what I use most. PU glues (expanding glues) also work well but cause a big mess and can bond to the finish. PVA based glues clean up with water so make for an easy life.
Step 2: Assessing the Damage
First of all get rid of the strings, you want no tension on the neck at all.
As you can see in the photos the break has separated the fretboard from the neck. This makes it a possibly more complicated repair. If the fretboard had lifted past the break line it would need to be removed and re glued.
If anyone would like a tutorial on removing a fretboard let me know in the comments (it's super easy!)
Note: With any repair there can be unique issues, it's a good idea to try and find what happened and when. With guitar neck repairs the faster you act the better. I have had one instance in the past where a person kept a broken guitar in parts in a duvet under the bed, this caused the neck to twist making the repair significantly more difficult.
Step 3: Tap Off the Nut and Remove
First remove the truss rod cover with your screwdriver and release tension on the truss rod with your Allen key.
Next with a mallet you can gently tap off the nut towards then headstock. If you are worried that the nut has been glued in you can take a scalpel to the edges to break the glue line.
Then you can gently remove the headstock with your hands pulling it out gently .
Note: In most cases the headstock does not need to come off but this one was quite bad.
Step 4: Block, Glue and Clamp
So for this stage I used a block of scrap wood (sapele if your interested) and cut a rough neck profile in on the bandsaw.
Note:It's a good idea to use a relatively hard wood for this as it will have a lot of pressure going through it.
Then place a scrap of material in profile cut in the block and cover both broken faces of the headstock in glue and clamp.
Note: Once clamped leave it alone for a good 24 hours!
Step 5: Done
At this point you can put the nut back in place with a small drop of superglue, reattach the truss rod cover and string the guitar back up.
I did this repair six years ago and the guitar is still going strong, it's an easy repair that people often charge a lot of money for.