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Do you guys use a caliper or some type of ruler?
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For viewing/measuring relief, just put a capo on the first fret and depress the string at the 13th fret. The string serves as a great straightedge. As SMS the machinist said, it’s hard to get a very accurate reading, but you generally would gauge it or eyeball it at the 7th fret.
For measuring action, the best thing I have found is a cheap little 1/64 inch scale ruler with a little sliding “T” on it. You can use the little “T” to pretty accurately see the action height by rocking the ruler back and forth on the fret and viewing from the side. The little “T” makes it easier to see wen you are higher or lower than the bottom of the string. I can’t get feelers in there accurately.
Here’s some Martin specs (I’m looking them up in Dan Erlewine’s book)
Max relief on 7th to 9th frets: .010
String height at 12th fret: bass E: 3/32 min to 7/64 max
on the treble E: 1/16 min 5/64 max
String height at the nut, measured from the bottom of the string to the top of the first fret Bass E: .024 max, Treble E .016 min (I never set the nut using measurements, but that minimum on the treble seems kind of odd to me)
I pass those along for reference, as you can see, there is quite a range of acceptable (per Martin) action adjustments. The bass E of 3/32 is nice action, but when I can get a bit lower without buzzing, I’ll do it. 7/64 is pretty high, and based on your picture with the quarter on the fret, I would guess you are lower than that. On the flip side, I think it could be likely be set lower. I take it you have a glued in saddle. I would first look at the nut and your relief. You may be able to have the nuts slots lowered a bit. Almost all factory setups I have seen have the nut set kind of conservatively. Once I get the nut set well and the relief to where it’s just barely buzz-free, I am generally pretty happy. Even if I don’t have a glued in saddle, I do as much without losing saddle height as I can. At some point, as the saddle gets lower, volume and tone starts to fall off.