MIMF

I've been just using feeler gauges and a straight edge which works just fine but kind of a hassle going through all the gauges trying to find the right one. I've considered trying the neck relief gauge from Stewmac, which is a bit pricey, but I think might be worth it as much as I would use it. but it looks a bit short for what I would need. It looks like it's designed for a truss rod that ends in or around the headblock. My truss rods go to the end of the fretboard and are accessed through the UTB. I use a sort of floating fretboard so I believe the entire length of the fretboard is in play here, not just the 1st through 12th. Am I really getting an accurate reading with a stewmac gauge? or is that only half the story?
If I do need something longer have any of you come up with a tool to accurately measure this?

I never measure it. Been doing it long enough that I can judge it by eye. I aim for .007". I can usually tell if it is more than .010" or less than .005". My frame of reference is the thickness of a business card. I use an 18" machinists straight edge which bridges the entire fretboard, but I prefer a bit of fall-off on the fretboard above the neck joint.

Instead of finding exactly the right feeler gauge that fits snug, maybe just use a .005" gauge and judge the relief based on how sloppy the fit is with this one gauge.

I don't measure relief carefully. I use "about the thickness of a business card" as a starting point and tweak the rod (when I do the final setup of the guitar many weeks after completion) until it seems right for that guitar. For me, it's eyeball and then feel--how it plays. Enough relief that I don't get back buzz and not so much that the guitar doesn't feel silky to play. I guess I ought to measure a few when I get them to that point and see if they all come out the same, but I don't think they do, so I haven't worried about it.

Great minds think alike, heh?

I had extra thick business cards printed up in case I ever need need them for a setup.

hmm... so it would appear that once again I am overthinking things.
That's actually how I usually do it too but I wouldn't admit it because I figured you guys would think I was being lazy and too imprecise. so, stewmac's neck relief gauge, not worth it or necessary. got it. Thanks

I just fret at 1 and 14 and use a special go/no-go gauge I made, called "looks like some, but not too much" Seriously, I just look at it.

I use the string as a straightedge. Capo it at the first, and then hold it at the body/neck intersection. Can tell really easily how much relief it has.

.004 is about the thickness of a sheet of printer paper...1st and body fret method, any visible space is more than that, so too much for the majority of guitars I set up. No movement at all is too little, so just a little movement at 8th is going to be within a thou.

My only trick is to go up the board fretting, with one hand, odd and even numbered adjacent frets and with my other hand tapping the string down over the middle fret to hear or feel a click letting me know if there's an issue in that specific area of the board. A little click tells me that there's about .0005" of relief between those two frets. Any high or low fret is immediately obvious.

David, that is a great trick!

I kind of get the impression that guessing the relief by eye is perceived to be a virtue ... I prefer to measure and know exactly what the relief is.

I use a 13" long straightedge which spans the first and fourteenth frets on any scale length and stick feeler gauges underneath to measure the action exactly. I do realize that you can set up an instrument satisfactorily without doing this, but I like to have a documented record of exactly what the relief is when I hand the instrument back to a customer ... just as I document the action at the twelfth fret and the height of the strings off of the soundboard at the bridge.

Use what works for you. You may not believe me, but I learned during 40 years of setting up guitars (and a brief stint as a machinest) that I can judge small gaps by eye and estimate the measurement to within one or two thousandths. I don't know if that is an extraordinary skill or just a trained eye that others may also have.