Here is a Gibson with a severely broken neck. This is actually the third time this guitar has fallen and suffered a broken neck. You would think the owner would have bought a stand considering this is his favorite axe. This guitar was sent in from another shop because the severity of the damage is beyond their comfort range as far as repairs go, so I will repair the structural damage and apply a finish to the neck and return it to them for any necessary fret work and final assembly/setup.

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Once I remove some of the heavy finish that was applied we can see some of the previous repair work. This included a set of splines. They appear to have been part of the first repair.

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One of the first things I do in these situations is conduct a forensic analysis and map out all of the cracks and breaks, including those that were repaired previously and have held. This shows me exactly what I am working with and around. It also shows me how the previous repairs held up and allows me to learn how to make better repairs. The first break appears to have been the classic one right at the heel, making the famous Gibson smile. This appears to have been made when the splines were inserted, as while it is not marked in this photo, I noticed later as I was cleaning and prepping to glue up that the second set of breaks actually went through the maple splines. I personally would not have put any splines in a simple break such as the first one appeared to be.
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There was very little in the way of wood fibers holding this all together, and the only way forward in some of these situations is to complete the break. The shaft of the neck was also pretty badly shattered about 3”- 4” down from the end of the splines. This also involved the truss rod pocket to a large extent.

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I would like to give my thoughts on splines in neck repairs in general and this repair specifically. To every point there is a counterpoint and at the risk of ruffling some feathers, which is truly not my intent, I would like to present some of the counterpoints to these type repairs. If you look at the previous two photos you should notice the white lines I have marked down the shaft are very much in line with the pockets for the splines. These happened in the second break. Any time splines are used the risk of a splitting fracture like this becomes a real likelihood in the event of another mishap. This is helped in part by the fact that the truss rod channel also runs down the center of the neck, leaving very little in the way of continuous long grain wood fiber through the neck. 

In our case here, it was exacerbated by the fact that we have maple splines in a mahogany neck. I’m sure the thought was it would be stronger. This extra strength gave the splines a bit more leverage during impact and their added strength actually transferred the force of the fall up the neck. The splitting was also aided by the fact maple and mahogany have very different expansion rates and characteristics with regards to moisture content and relative humidity. This means that the pieces did not move in sync with each other and placed stress on the glue joints of the splines. maple actually shows greater expansion relative to MC than mahogany (although it reacts much slower) which means that at certain times the maple may have been so tight in the pocket that it actually acted as a wedge and may have even started to crack the neck before the second fall. The new breaks running down the shaft of the neck also generate from the spline pockets, both the ends and the bottom. 

Another problem here was that the spline on the treble side was not completely seated in its groove as we can see in the next photos. It became hydrolocked by glue. This left only the tiniest sliver of wood running up the edge of the neck holding that side of the fretboard. This could have been because the fit was too tight or just a plain excess of glue. Either way, it left a section of fretboard unsupported right at the very end. Something else that I don’t like, while it hasn’t been an issue yet, is that the top of the splines ends directly in line with the E tuner holes. Again, minimizing the amount of long grain fiber actually running through the area and weakening it. If it falls again, that is where I expect it to break.

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Don’t get me wrong, splined repairs have their time and place. They make very good repairs if done correctly. They should only be used in severe breaks where there is not enough long grain to successfully glue up. They should always be done with the same wood as the surrounding neck. Thinner is better than wider as this keeps them farther in from the edge and farther away from the truss rod pocket. They should only be as long as necessary to bridge the damage. Consider staggering the ends to lessen the chance of a new break happening at the ends in the future. Make sure they fit completely with no voids and use only enough glue to do the job. 

This neck is far beyond any type of splined repair. While I do not like the maple splines, at this time I see no method of redoing them and staying within the customer’s budget. So it is time for some structural epoxy. This has actually become my go to repair for anything beyond a simple break. The first thing I do is start dry fitting the pieces back together and looking for out of place fibers that are keeping it from closing up. These are either pushed back in place or removed with dental picks and an exacto. Due to all the splits running down the neck I will be using a compression wrap to force epoxy into them. I will then apply clamps as needed over top of this as well. This is all tested dry a few times with some measurements being taken along the way to check alignment until I am satisfied with the procedure and the results.

First, I cover the threads on the truss rod with some wax so they don’t get epoxy on them, being very careful not to get any wax on the wood as it would weaken the joint. I tape off the fret board and peg head face. I then mix up a few grams of epoxy. I use System 3’s T-88. I wedge open any cracks in the neck that I can and let the epoxy run into them for a few minutes. I coat the entire open surface and work epoxy into all the joints I can. I slip the neck back together over the truss rod and then wipe a medium coat of epoxy over the entire area. This is wrapped in a double layer of wax paper and then wrapped with rubber straps pulled tight. This forms a bit of compression and helps drive the epoxy into the cracks. Clamps are then added to pull the neck together lengthwise and apply a bit of extra pressure on the end of the fret board. The epoxy is left to cure for 24 hours and this is what we have when it is unwrapped.
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With a bit of scraping and sanding it looks like a neck again. It needed a little bit of filler in a few spots to even things out, but here it is wet with solvent being inspected prior to finishing.

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And here it is with finish applied. The rest of the neck was pretty beat and had some dings and gouges, including a large spot from where he leans it against his amp. All these were filled as well and the whole neck finished in a dark opaque brown to blend in with the outer portion of the burst finish on the body.

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Originally published in Brian Howard's Guitar Building & Repair Blog.