Neck Relief

The first step, after tuning your guitar is.. Wait a minute! You DO know that you need to tune the guitar before taking measurements or making any adjustments, right?

You see, a guitar is a combination of balanced forces and we can only get things properly balanced when the string tension is properly tuned. OK, now back to your regularly scheduled program..

You’ve checked out the photo above and now you’re thinking, “Hank, I don’t need to scavage string clippings from the trash to check string heights, I can afford a ‘string action gauge’!”

Guitar String Action Gauges

Well, here’s the thing, Bubba – that action gauge ain’t accurate enough for measuring just ten-thousandths of an inch. In fact, most of those so-called string action gauges are so inaccurate that they vary by 15 thousandths or even more, even among the same brand names!

The best action gauges I’ve found are the Fret Guru gauges, and they even vary by five thousandths. So how can you trust a gauge that varies by 50% or more of what you’re trying to measure?

Reading an Action Gauge

Here’s another cud to chew – you probably can’t read a string action gauge anyway! Look, I’ve trained guys who’d worked years as a tech for places like Guitar Center, Taylor, Dean and Sam Ash. You know what one thing they all had in common? They couldn’t accurately and consistently read a string action gauge.

Given the same guitar they’d just measured the action on a day or two before – a guitar that hadn’t changed a bit – they’d read five, ten, even fifteen thousandths differently!

And most times, none of their readings matched mine or my trained techs, even when they used a Fret Guru gauge!

To properly read an action gauge (after first getting a decent, accurate gauge!), you must have good lighting and have your line of sight perfectly aligned with the bottom of the string you’re measuring. It usually takes days for a trainee to learn to consistently get their readings correct.

String Clipping Gauges

We generally set neck relief at 0.010″ – that’s ten thousandths of an inch, with low-E fretted at first and last frets, measuring at the 8th fret for electrics or the 7th for acoustics. An experienced eye can somehow, pretty accurately, “eyeball” that setting. The rest of you should use a string clipping “gauge”.

The B-string from a set of nines should be 0.011″. That means you should get a gentle bend as the string goes between the string bottom and the fret top.

Truss Rod Too Tight

If the string won’t go through or if the bend is drastic, then you need to loosen the truss rod adjusting nut by turning the same way you would loosen any other nut. Now, some rods will have a wheel with holes and others will have a cross head, but the same principle applies.

Truss Rod Tools

Most rods take an Allen wrench. Generally 4mm or 3/16″ or 1/8″. You must be certain to use the correct size wrench that is in excellent (not worn) condition and have it firmly seated. Some acoustics will have that adjustment nut WAY back at the neck heel and you have to access it through the sound hole.

If you have a Gibson-style truss rod nut (some PRS and others have this type also), which is a male nut that requires a socket (female wrench), don’t try using your automotive socket set. You just have to break down and buy the correct tool. These generally come in three sizes and who knows what size yours takes??? So buy all three!

Truss Rod Too Loose

if the B-string clipping doesn’t bend at all, you’ll need to tighten the truss rod nut. Do not loosen the guitar strings! Drastically changing the string tension makes the neck change. Loosen the strings and the neck will straighten or even back-bow. Sure, it will make the truss rod nut turn easier, but it may have turned easily anyway.

If you bend wood for a minute or so, then release it, it probably won’t immediately go back to its original resting position. In fact, it may end up at a new resting position after 24 hours or so. Loosening the strings when adjusting the truss rod is like trying to shoot skeet with a snub-nose pistol!

Tighten the truss rod adjustment nut as you would tighten any other nut. Turn a little at a time while trying your string gauge. When it gives a slight bend while passing between the string bottom and fret top, you’re done!

If the nut doesn’t want to turn, or if it seems like it would take a lot of force then STOP! You can damage your fretboard by applying too much pressure.

Now might be the time to loosen the strings and set a thick book under the headstock so you can apply some pressure on the fretboard to “help” the truss rod, but a better idea is to realize that it may be time to take the guitar to a good shop.

Stripped Truss Rod

If your wrench turns but the adjustment nut does not turn, you probably have a stripped truss rod adjustment nut. It may be extractable but you’ll have to decide whether to YouTube it or go to a pro. There is a high likelihood of damage to your guitar during an extraction process.