Coincidently, yesterday I was brought two guitars with protuding fret ends. The first was an I****** midrange seven string guitar with a bound neck. The second was a lower end E** six string also with a bound neck. Both electric obviously. Each were indoor guitars that were stored where the lowest humidity was about 50% rH at ~70 degrees F. The normal humidity here varies between 70-90% year round. Both had unfinished ftretboards. Both the guitars were midrange guitars (500-800$).

The fret ends protruded inconsistantly from 0.025" to 0.010" beyond the fretboard and binding. Not all had torn through the binding (more on that in a minute). The worst frets were #'s 4,5,7,9,18,&24. This was first measured with my Starrett caliper then with my Micrometer (calibrated in September).

Examining the guitars closely, you could see that some fret ends had penetrated the binding and others were still completely covered up. This gives clues about how these guitars were constructed (others use different sequences) that impact how the fret ends penetrate (or not) the binding. A careful examination, gives the conclusion that the fretboard with fret slots is set on the neck and then the binding ledge is cut.

This is where the problems begin. It appears that the frets are then set. What looks like it was supposed to happen is the fret ends are trimmed (either to the edge of the fretboard or just beyond). Clearly here they were trimmed unevenly (hence the variability in measurements above) and the inconsistant penetration of the fret ends ainto the binding.. I suspect also that the fretboard and neck were not fully kiln dry when assembling and have shrunk. The binding was then set and a crown, trim, and end shape was performed. The workmanship was pretty poor (inconsistant shaped ends, poor filing /sandinding, etc). This left me to mask off and trim / file the offending ends. I also had to re-set a few frets that were proud of the fretboard.

From both of these examples, I found that the work of trimming the fret ends prior to setting the binding was poor. They weren't trimmed to the end of the fretboard. Some were still proud. The binding when settting is set with a glue that softens the plastic are part of the adhesion process. This softened binding allows the protruding fret end to penetrate the binding.

What do I conclude from this:

1.) In these cases, the Humidity had nothing to do with the expansion / contraction issues and fret end roughness. (Sorry, I don't see 70% at 70 degrees as low humidity). It is also beyond reason that a humidity change would have a fret end protruding 0.025" across 2.125" (widest dimension of this fretboard). The other 20 guitars kept in the same rooms and cases were unaffected.
2.) There is a clear lack of workmanship and precision in the manufacture of these particular instruments (inconsistant protrusion of the fret ends. I believe this to be the result of bad trimming after setting the frets.
3.) The fret work was poorly done (frets needing to be re-set, poor trimming, and inconsistant fret end shaping).
4.) Given that all frets protruded to at least some degree and frets had "popped", I think it likely that the fretboard was not as dry as it should have been when assembled. I believe the fretboard continued to dry and shrink after construction. The manufacturers tried to address this by sanding the neck edge after (you can see where the binding had been half cut down by sanding). Obviously, I cannot prove this as I have no assembly MC nor do I want to damage anothers' guitar to get a current MC. Still, I think it probable.