There are fundamental problems with a constant curve from fret 1 to fret 22. Modern fretting which facilitates deep bending in the higher numbers actually programs flat boards or boards with drop away from the 15th fret (or thereabouts ) to facilitate a good take off angle and clean notes from the fret crown to the bridge as you bend a straight string around a curve. The truss rod has very little command after the 12/14 fret anyway and any curve upwards after that is known as "rising tongue" and is generally eliminated where possible.
This constant curve thing shown guarantees a rising tongue and string choking as does the piecemeal and unrelated leveling across the board when a constant radius is vital for consistent bends and volume.
Furthermore, finishing a fret with longitudinal sandpaper strokes invites the strings to grate across minute corrugations left by this method. Not only do string grate but bend with vibrato technique is inhibited because of induced string drag.
We fret level with machined full and partial length cauls and finish refrets and touchups with micromesh parallel to the fret because that's the way the string slides when bending.
To persist in dissembling this method is to invite dissent by well meaning defenders of Youtube backyard warriors. The answer from me is: no I don't work like this and this approach is unsuitable for technical/heavy rock playing which is what this AFD Gibson was designed for.
However, bass necks with problems (compression "S" deformation for instance) present different challenges and sometimes leveling under string tension is a necessary thing. That's another subject.
"To persist in dissembling this method is to invite dissent by well meaning defenders of Youtube backyard warriors"
Your whole post summed up my thoughts, really. In his defence, he works almost exclusively, it seems, on budget guitars. However, it doesn't appear to be any quicker than any other traditional method.
1 hour and 39 minutes? I don't have the time!
if you think about it for a minute, this could only work if a neck with any relief described a perfect arc out of a circle that you could then match with an identical circle arc with that bowed leveler thing.
since neck relief curves are more likely ellipses (more curve here, less curve there) and it's impossible to slide one non-circular curve perfectly along another, there's no way that method can be accurate. like @Russell Vance was saying, up on the higher frets you might have no curve at all, so leveling them with a fully curved stick would make a mess of things.
i suspect that thin little stick flexes enough to eventually hit most of the frets regardless of the neck curve, averaging out the errors enough to result in something sort of usable.
i am a firm believer in accounting for string and truss rod tension when leveling, but i go with the idea of adjusting to zero relief (while strung), locking the neck into that precise state with a tensioning jig, leveling with a flat beam to the goal of perfect flatness, then relaxing the truss rod afterwards into the slight relief needed.
Anyone here using the Katana® fret-leveling system? As I understand it, it's basically a set of long thin aluminum leveling blocks, each with an integrated trussrod to "build in" relief to a already-fretted neck.
Supposedly, it works with the strings on and up to tension, but (to me) it sort of sounds like a solution in search of a problem. Just curious if there's much "in the trenches" experience with it here.
same thing, same problem.
i can see a niche for "strings-on" leveling as long as the leveler is dead-flat and running over a neck also adjusted for max straightness.
as soon as you put relief in the neck you likely don't have a perfect circular arc, which means a curved leveler will not actually "fit" sliding down a curved neck profile.
I have tried similar processes - and a lot others - during the years of finding the best universal leveling method.
IMO, it can create more problems than it solves.
I have settled on the tried and tested straight neck, leveled with a straight beam. It always gives consistent results and the possibility for very low action. I also have a neck jig, but seldom use it because I don't find it gives any advantage over the traditional method.
I work with low tension steel strings on old parlor guitar with no truss rod. Necks on these guitars can be stiff or soft depending on the neck wood and thickness. I always put in a carbon fiber rod in the neck to get a somewhat predictable bend when stringing up to tension. The neck is warmed straight if it is bent and after gluing back the fretboard the neck is dead straight. Next step is to fixate the guitar in a jig with strings at tension and temporary frets. Then off with the strings and frets to be able to sand the fretboard to a nice even relief curve.
I bough the Katana to do that work, but realized that the curve is not perfect. I have a friend with a CNC who cut a 0.10, 0.15 and 0.20 mm relief curve in a couple of square aluminum bars. I put on some sticky sandpapers and use them to sand a pretty perfect relief curve into the fretboard. I finish off with a bit of extra sanding on the fretboard on top of the top to make a minimal slope off.
The neck will have a slight upbow after letting it loose from the fixating jig. Also, depending on the angle of the strings over the nut, the upper part of the fretboard will have an even bigger back bend from the rotation force of the strings over the nut, from the nut to about the second fret.
The frets are put on and the guitar goes into the jig to fixate it with strings at tension a second time. Now I can do the final fret work using a finer sandpaper on the same aluminum bar with the cut relief. With strings at tension the neck will end up having the relief I sanded in the fretboard and on top of the frets. It pretty much stays that way, the carbon rod will keep the bending with time to a minimum.
I use the Katana as a quick fix for crowning uneven frets on cheap guitars, it works good enough for that purpose. I don't have to use the fixating jig and can do the work a lot faster. With serious fretwork on modern guitars with a trussrod I prefer to adjust the trussrod to a good relief first of all and use the relief aluminum bars on the fretboard and for crowning the frets.