Measuring your guitar’s string action seems like a pretty simple deal, right? I used to think so, too. Until I discovered that my new apprentices weren’t getting the same readings that I’d get. They weren’t even getting the same readings on the same, un-touched guitar that they’d gotten the day before!
Guitar String Action: Measure or Not?
Before I continue, yes I know there are a ton of you out there who don’t believe in measuring action, relief, nut slots or anything guitar-related.
If you’re only working on your own guitars, I suppose that’s fine. But if you’re working on other players’ guitars, you have to measure to give consistent results.
You might be surprised to learn that a survey of “professional guitar techs / luthiers” showed that more than half do not measure string height! Most say they just go by “feel” or “noodling”.
That’s likely the reason for the major complaint I hear about other shops – “Their setups are sometimes great, sometimes just ‘ok’ and sometimes lousy.” That first “lousy” setup is likely the last time the customer goes to that shop!
Your preferred string action for any particular guitar, is what feels right to you. The fact that it felt good for some noodling tech, is irrelevant.
A five-thousandths of an inch difference in action can be the difference between “Great” and “Lousy”, and I doubt that many humans can “noodle” to within a few thousandths of an inch!
In twelve years of setting up roughly one thousand guitars each year, I’ve learned that there’s a “bulls-eye” for action height that satisfies about 98% of players, with the remaining few asking for no more than a five-thousandths adjustment from that bulls-eye!
Measuring String Action: When?
Let’s take a short “train ride”. I’m referring to the wreck called the “T.R.A.I.N” setup system. Here’s what it stands for:
- T: Tune
- R: Relief
- A: Action
- I: Intonation
- N: Nut
This is the sequence that over 90% of guitar techs / luthiers use when setting up a guitar according to a survey recently taken on the Facebook group “Guitar Setups & Repair”.
The problem with that system is that it defies physics!
You see, whatever height change you make at either end of a guitar string, affects string height at the 12th fret by fifty-percent. That’s just physics. If anyone has a problem with that, they should take it up with Mr. Pythagoras.
By setting string height (saddle height) before setting nut slot heights, you have no idea what the string heights will be when your client picks up their guitar.
Example:
Say you set the action as low as you can go without buzzing. Maybe 0.055″ on low-E, 0.050″ on high-e. Next you file the nut slots down. They’re typically high on new guitars, so let’s say you take them down an average of ten-thousandths each.
I’ll grant that you haven’t changed intonation much, if at all. But you definitely just lowered string action at the 12th fret by 0.005″ and now it’s gonna buzz!
Since we measure nut slot heights by fretting (usually at the highest fret), the saddles are taken out of the equation. That’s why nut slot heights aren’t affected by saddle height changes and it’s why T.R.A.I.N. risks a train wreck!
Measure String Action: How?
Your customer says he likes his action from 0.070″ to 0.060″, low-E to high-e. Got it? Maybe not. Are they measuring at the 12th fret, the 17th fret or somewhere in between?
If your customer measures at the 12th fret and you measure at the 17th, he’ll receive a guitar with action a bit lower than he’s used to. And vice-versa if you swap frets. This is because string height gradually increases as you go toward the saddles.
But even if you both measure at the same fret, your results will likely vary! This is because most people, even many techs / luthiers, don’t understand how to properly use a fret gauge.
You’ll only get a correct reading if your line of sight is on a plane with the bottom of the string. Even a slight difference in viewing angle can easily result in a +/- 0.005″ difference.
In my experience, it takes an apprentice from one to three full days of practice, to be able to consistently get correct readings from string gauges when measuring string action height (saddle height).
I should make it clear that I do not recommend action gauges for measurements below 0.020″ (twenty-thousandths of an inch). To get accurate and consistent measurements at such small amounts is just not feasible.
We recommend string gauges for nut slot and relief measurements, which are readily available from your string clippings. We’ll cover use of string gauges in a future article.
Measure String Action: Where?
Google, Facebook, YouTube – they’re all over the map with advice of which fret to measure string action at, with most choosing the 12th or 17th fret. Allow us to clear up the confusion right here and now –
Guitars with scale lengths of 24.75″ (Gibson style) should have their action measured at the twelfth fret. Guitars with 25.5″ scale length (Fender style) should be measured at the 17th fret. As I recall, Dan Erlewine concurs in his famous guitar setup book.
But rarely is the reason given for the difference. Well, here it is:
A 24.75 inch scale length generally needs a slightly higher action compared to a 25.5 inch scale length, as the shorter scale length results in less string tension, making the strings more prone to buzzing against the frets if the action is set too low.
ChatGPT
By setting action at the 12th fret, you’re automatically making it slightly higher, relative to scale, due to strings gradually rising as they near the saddle.
To put it another way, if you like your Gibson 24.75″ guitar set at 0.070″/ 0.060″ at the 12th fret, then you’ll likely like your Fender 25.5″ scale the same height measured at the 17th fret.
Which String Action Gauge?
I have a cheap, Rizo, easy-to-read, action gauge that’s pretty accurate. The problem is, I went through about two dozen of them to find that one, almost-accurate gauge. The gauges – all Rizo and apparently identical – varied as much as twelve-thousandths of an inch!
Our shop has tried about a dozen different brands of string action gauges, striving for accuracy and consistency. We now insist that all our techs use just this one brand of action gauge: Fret Guru.
These gauges don’t seem to vary more than two or three thousandths of an inch and we’re able to get consistent readings between all our tech using the FretGuru Precision 8-in-1 String Action Gauge.
We don’t accept freebies or payment for reviewing products, but Bernie from FretGuru is offering our readers a 15% discount when using this code at checkout: guitarsdoneright15
String Action Gauge Summary
- You can’t manage what you don’t measure.
- It takes effort to train yourself to properly read a string action gauge. The slightest off-plane angle of sight will guarantee an inaccurate reading.
- Measuring must be done after a sequence of previous events.
- Measuring at different frets will give different results.
- String action gauges can vary wildly in accuracy – choose the right gauge!