I looked at a quarter… mine came out to 0.067". That’s a hair over 4/64 (or 2/32), which is quite a bit lower than how I set mine measuring the low E at the 12th fret (back to the original post, my mandolin is actually a bit lower than a quarter on the low G string 12th fret). The way I play, if everything on a guitar (frets, nut, saddle, relief) is dead perfect, the lowest I get (for my playing style) is approaching 5/64" (0.078"). There are a couple factors that go into the question of “what should I do with it.” One is how you play. Some people who play lightly like a very low action (like electric action). I have found I don’t like electric-like action due to the fact that my attack is too strong for that and I like the tone I can pull out of a slightly higher action. The other thing to consider is that the numbers we are talking about measuring are very small… one person might say their guitar measures 5/64" and someone else might say it’s 4/64" or 6/64". My point is, without measurements in a known way or knowing how you play, it’s hard to say “yep, it’s too high” or vice-versa.
As far as what you describe with your guitar here’s a few thoughts:
Light buzzing at the first fret - it could be a an issue with the fret, but most likely a tad more relief would eliminate it.
High action up the neck - Action is set with the nut, the saddle and the relief. I would set the action at the nut first… that is almost totally independent of the other 2 items. Most guitars I have seen come with the nut action set too high. If you don’t have nut files, a trip to a good local luthier may be the easiest way (and it’s less expensive than buying the nut files). Setting the relief is straight forward… I try to get my action set with as little relief as I can get away with. The last item is the saddle. I am guessing you have a drop-in saddle and if so, they are easy to modify (and you can keep your original untouched as a backup). Frets.com and other places on the web have great information on doing setup.
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