This one’s for my fellow woodworking nerds out there: converting a bolt-on to a set-neck.
Our pal, Anders Osborne comes into our shop with unique requests on a fairly regular basis, but this one takes the cake. He had a custom Delaney guitar built for him using some cypress siding from his house that he’s been hanging onto since it was ravaged by hurricane Katrina. Mike Delaney used the cypress for the top and Honduran mahogany for the neck and body. The guitar sounds killer and really means a lot to Anders – especially since it was built to replace his stolen ’68 Les Paul Deluxe. But there was always something missing about the feel and the sustain of the instrument, and he was convinced it was due to the guitar having a bolt-on neck, as opposed to a traditional Gibson style mortise and tenon set-neck. So he brought it in to talk about converting a bolt-on neck to a set-neck.
There’s nothing wrong with bolt-on neck construction, but it has different tonal characteristics than a set-neck. A bolt-on has a brighter, snappier attack on the front end of a note, due to the string vibration transferring through four metal screws and a metal plate. It’s a great sound synonymous with that classic Fender tone, but it lacks the resonance and sustain that a set-neck has when the two pieces of wood are bound by glue. Anders was looking for the latter in this guitar, so I figured out a way to make it happen for him.
I removed the neck and sketched up a plan for cutting a mortise into the neck pocket. Then, I sanded the area flat to give the impeding neck heel a square mating surface.
Using our trusty Festool plunge router, I made the first irreversible cut. Point of no return.
That was the easy part. The next phase was to fabricate a neck heel/tenon. I decided to make two small dovetail joints flanking the truss rod, so I glued up a three-piece quarter sawn Honduran mahogany block to match the existing neck lamination.
Then, I cut the dovetail channels into the neck and the tenon block. These cuts have to be dead-on, otherwise the laminations of the neck and heel wouldn’t line up, and that’s no good.
Once the dovetails were fit, I cut and shaped the tenon into the other side of the block.
After I snapped the test fit into place and it looked good and well seated, I glued the tenon to the neck.
Setting a mortise and tenon neck angle is basically the same process as setting an acoustic guitar dovetail joint. For this guitar, I set the angle of the heel to align with the Tune-O-Matic bridge at it’s nominal point in up and down travel, and centered the string lie to be symmetrical with the neck edges.
Once I got the neck angle where I wanted it, I carved and shaped the neck heel. This is much easier to do before gluing the neck to the body.
Since it used to be a bolt-on, I just used the existing screws and holes to glue and clamp the joint. Worked out perfectly!
I let the glue joint sit over the weekend, then took the screws and neck plate out and doweled the holes, first by recessing 1/8″ dowel rod, then capping the holes with mahogany plugs following the grain pattern.
A few coats of gun stock oil later and she’s good to go!
The conversion definitely made a noticeable tonal difference, and now the guitar has the Les Paul vibe Anders was going for. What a fun project and a cool guitar!