This is a particularly handsome Heritage 535. It would be even more handsome if it were in one piece instead of two, though. The neck's come off and a little bit of investigation shows that it never stood a chance. This neck joint was weak from the start.
These joints are referred to as 'mortice and tenon' joints. In this case, the tenon (the bit at the end of the neck) was too small for the mortice (the 'pocket' in the body). As well as having a relatively large shim on one side, the tenon didn't make contact with the bottom of the pocket. There's an gap of a couple of millimetres between the two.
You can see the circled bits in the image. On the left is a chunk of mahogany from the tenon that's split off and the glue line is visible on the right. You can see the gap.
That gap means no glue joint there. Only the sides are glued (well, those and the 'face' of the joint but that's not providing a lot of strength).
This is a weak neck joint that was much more prone to fail that it ought to have been.
Rather than just gluing it back together, I'm going to build up the tenon to get this joint to where it should have been from the factory.
First off, that little chunk of mahogany that's still glued to the side of the neck pocket has to be removed and glued back to the neck tenon. Once that's done, I nab a new bit of mahogany and thickness it so that it will fill the gap.
In the right photo, you can see I've glued this on and cut it to match the shape of the existing tenon. The thickness of the added wood gives you an indication of how much of a gap there was.
I removed the old glue from both parts and re-glued the neck to the body. Because the break was quite clean, only a little touch-up work was required to get the guitar looking its best.
This repair looks good and, importantly, has actually resulted in a better, more sound, neck joint than when it left the factory.