How do we decide if a guitar needs a neck reset? Returning to our box fresh guitar, if we were to trace a line parallel to the fingerboard you can see it would sit nicely on top of the bridge. Assuming the guitar has been build in standard fashion, this is is the neutral neck angle we’re looking for:
In the real world, we check this by getting the neck as straight as we can using the truss rod and careful observation with a straight-edge or two. Then, resting a long straight-edge on top of the frets, we project out to the bridge. If the straight-edge lands on top (or a little above) the bridge, we should be OK. Anything else: you’re usually looking at a neck reset and/or measures to reduce misshapen body geometry: using a Belly Doctor, adjusting humidity, repairing braces and so on.
This is our Epiphone:
Our long aluminium straight edge just about brushes the top of the bridge. We’re in luck! You should carry this test out both with and without strings.