Let's take a look at a neck reset that threw up some curveballs along the way.
On a Gibson acoustic guitar, the job of getting the neck off is generally a little more work. As well as glueing the actual dovetail joint, the folks at Gibson also apply glue to the surfaces between the neck-heel and body-sides. Also, they glue the neck in and then lacquer neck and body together. This means getting through the lacquer safely when removing the neck, and—more often than not—means some light finish repair work after it's all reassembled. A Gibson is more work to reset but is still generally straightforward.
First up, this guitar has a couple of longitudinal cracks in the top. These have been there a while and have had a previous repair before I got the guitar. I check the repair and it seems sound so I move on. I also note that there is a small gap between the bottom of the heel and the body-binding. I can't tell too much about this now and it's clearly been there for some time so I pop it in the mental notebook.
I won't go into detail as I've covered much of this before. I free up the fingerboard extension, drill my steam access hole and get to work.
Something's not right.
As soon as I give the instrument its first 'encouragement wiggle', I can tell that something is wrong.
After some investigation, the issue becomes clear. The neck block (the solid hunk of wood that supports the neck inside the guitar) has become loose. The guitar's top and back are no longer glued to the block and any pressure I might apply to remove the neck is also going to push the block up against the top until it breaks.
It seems likely that the existing top cracks happened either because the block was loose and not properly supporting the top or (more likely) occurred at the same time as the block became loose—probably in a fall. Either way, I don't want to make things worse.
You'll notice in the photo above right that I've removed the fingerboard extension (and that palate knife shouldn't be able to slide in like that). However I proceed on this job, I need to re-glue the neck block but I'm now concerned about unduly stressing this guitar top any more than is completely necessary. Removing the fingerboard extension will allow me to support the top as I remove the neck.
You can see that support in the photo on the right. The dovetail-shaped slot cut in some plywood lets me ensure that the top doesn't move as the neck joint is separated. That separation is a slightly slower job now, and a more careful one.
Once the neck is out and I've cleaned up the joint, I can glue the fingerboard extension back on to the neck (using a sliver of rosewood to take up the space of the fret-slot I used to cut through. This slot will be re-cut after things are back together. I go though the normal neck reset process from here.
This Gibson has one more curveball to throw at me though. As I alter the neck angle, the bottom of the joint becomes looser in its socket than I'd generally have expected (a little is quite normal). Turns out, this dovetail's not the best fitted joint I've ever seen. The dovetail (the male part of the joint) is quite a bit shorter than the socket it mates to. I'm going to hazard a guess that this may have contributed to that little gap between heel and body-sides I mentioned earlier.
Not a major problem. Some shimming is pretty much always necessary during a dovetail reset. Done properly and I've got a heel that contacts perfectly all around.
Better than original. Nice.