How I Use A Backstrap to Fix Broken Headstocks

Gibson headstock breaks are unfortunately a fairly common repair. The transition between the neck and headstock leaves relatively little long-grained wood in an area that is subjected to a lot of stress from string tension, making it particularly vulnerable to break if it gets a hard knock or drop.

This particular Les Paul had suffered a fairly severe break, and sections of the headstock were missing. Rather than simply gluing the break back together, the customer and I decided that the best course of action would be to reincorce the back of the headstock with a fresh piece of mahogany, otherwise known as a 'backstrap.' Sometimes luthiers do a 'splint' repair for Gibson headstock breaks, where two channels are routed into the back of the neck to act as a reinforcement. I've had a few guitars in that have had splint repairs in the past, and I have found that over the years the splints can expand, and you can feel them with your thumb. Between this issue, and the fact they can sometimes look a bit odd, I always opt for the backstrap method.

Re-building the broken headstock

The first job was to get the broken sections of the headstock properly aligned and glued back together. Quite often you find loose fibres of wood that need to be carefully picked out to make sure that the two pieces fit back together nicely. If you don't pick out these fibres, they can cause the join to not close properly, but if you take too much then you lose a lot of wood to wood contact. It's a fine line, so a lot of time is spent preparing the two pieces to fit well.

There was a large chunk of the headstock missing, so I had to graft in a fresh piece of mahogany. Since I'm now working with fresh material, it means that I can use the chisels to cut a nice and flat wedge into the headstock. A piece of mahogany is then made to fit the wedge before it's glued in with Titebond.

Preparing For The Backstrap

Once the structural repair was complete, I could prepare the back of the headstock for the backstrap. I used a safety planer in the pillar drill to carefully skim a small amount of material from the back of the headstock - around 2mm. I then set up a fence on the bobbin sander to blend the back of the headstock into the main part of the neck.

The back of the headstock and neck were then cleaned up by hand using small sanding blocks and scrapers. The goal here is to make the back of the headstock nice and flat, while maintaining a smooth transition as it blends into the neck. I'm also keeping an eye on the thickness of the headstock at this point, because the tuners won't fit if the headstock is too thick by the end of it. You might have noticed this gutiar had the 'RoboTuners,' which we decided to remove in favour of some Spertzel locking tuners.

Making and fitting the backstrap

The backstrap itself was made from mahogany and was approximately 2mm thick to make up for the material that was removed from the headstock. Mahogany was chosen for this repair simply because it matches the neck material, and the closer the colour match, the more invisible the finsihed repair will look after all the colour work has been completed. I do offer to use ebony for these repairs as it can be quite a nice contrast, but more often than not customers prefer for their instruments to look as close to original as possible. The transition between the headstock and neck isn't very sharp (around 14°), so the mahogany is lightly bent on using a hot bending iron until it conforms to the proper shape.

Getting a good glue joint over the entire surface is critical, so below is my clamping method for glueing backstraps. Because I used the bobbin sander and the fence to rough out the transition, it means that the rubber section from my bobbin sander was almost a perfect match for the shape of the back of the neck. I use a couple of cauls either side of the bobbin to glue down the flat surfaces, but also to secure the bobbin in place (cylindrical objects like to slide around.)

Once the glue had cured, the backstrap was carefully brought down to the shape of the original neck. The edges were blended into the surrounding mahogany, and the repaired areas were cleaned up in preparation for finishing.

The result is a relatively unobtrusive reinforcement that adds considerably more strength to the vulnerable neck-to-headstock transition while retaining the feel and appearance of the original neck.

Finishing and setup

With the structural and woodworking side of the repair complete, I dropped the gutiar off at Stephen Devine in Glasgow, Shawlands for the finish work. Stephen is an absolute expert in all things finish, and always does a fantastic job.

Once the guitar returned to the workshop, I completed the final setup and made sure everything was playing as it should.

Headstock breaks can vary enormously in severity. In this case, the combination of the original break, the missing sections of mahogany and the additional backstrap made it a fairly involved repair, but the finished guitar is once again ready to be played without the original weak point being left unsupported. Happy days!