Broken headstock glue ups are tricky, especially if the headstock is completely broken off the neck. The headstock needs to be aligned to the neck , and the headstock and neck need to be pushed tightly together to avoid having a gap along the break line. If you have a Proper Guitar Workstation, check out the headstock jig James Roadman built here: https://www.instagram.com/p/DFawFcDuTuB/?img_index=1. If you have a small workspace like me, the headstock jig here may be an alternative for you. The best part is all the hardware should be available at a hardware store for under $10 US.

The Fusion 360 files are all parametric. You can customize any part with the parameters listed under “Favorite” in the Change Parameters list. If you want to do further customizations though, you can always modify or add to anything in the timelines.

To customize the Neck Clamp, measure the width of the fretboard at the 2nd and 3rd frets, or the 3rd and 4th frets. The clamp is designed to fit between either of those sets of frets. I add 2mm to the fretboard width measurements, and 1 mm to the fretboard depth measurement to account for lining the caul with cork to pad the contact area with the back of the neck. The rod slots in the clamp allow you to adjust the angle of the rods to match the plane of the headstock.

To customize the Headstock Cap, use either the RoundHeadstockCup.f3d or SquareHeadstockCup.f3d – whichever more closely matches the profile of the top of your headstock. Change the parameters for the headstock width (hdstkwidth) and the headstock depth (hdstkdepth), and you are ready to print.

As an example I did the parameter customizations for a Les Paul Standard. The customized files all have the name prefix “LesPaul…”. There is an additional file for a clamping caul that I added for extra insurance that the bottom edges of the crack were flush with each other. I covered the surfaces with clear packing tape to make sure the caul didn’t get glued to the neck.

Everything with the exception of the Headstock Cups can be printed using PLA with 10-20% infill. In this case a little flex in the parts is ok. The Headstock Cup should be printed using TPU to avoid damaging the headstock finish (even more than it is already). If printing with TPU is not an option, you could increase the headstock width and depth parameters to allow for padding the inside with cork or some other padding material.

You may encounter a partial headstock break that is “hinged” on the face veneer of the headstock, has been broken for some time, and the crack does not want to close. In that case it may help to push the headstock in the opposite direction (think of a broken bone traction device). In that case you can customize the LesPaulHeadstockCollar.f3d instead of one of the HeadstockCup files. I’ve included an image of the Collar in use.

I used 1/4-20 hardware, but you can substitute 7mm hardware. The nuts are glued into the knobs.

Parts:
2) 14″-15″ lengths of 1/4-20 all thread rod
10) 1/4-20 nuts
2) 3″ or 3 1/2″ 1/4-20 carriage bolts
cork sheet for padding parts