What is the right way to adjust a truss rod at the heel?
This is not that big of a deal once you know how to do it.
I recently performed a truss rod adjustment on my Yamaha RBX170 electric bass which does have the truss rod adjustment hole at the heel. However, I'm going to explain one step beyond that for Fender guitars, such as the Fender '60s Jaguar seen above, where the neck physically comes off the body in order to adjust neck relief.
Which way does what?
Assuming a right-handed instrument in the seated position, a clockwise turn a.k.a. "turning right" a.k.a. "turning down" tightens the truss rod.
Assuming a right-handed instrument in the seated position, a counterclockwise turn a.k.a. "turning left" a.k.a. "turning up" loosens the truss rod.
On the RBX170 bass, the neck is not required to be removed to adjust relief. Yamaha put a slot at the heel that can fit a wrench in there to make adjustments.
This is what it looks like (see the arrow I added in that points out where the slot is):
If holding a right-handed RBX170 bass in the seated position, "turning down" is a clockwise turn, which tightens the truss rod and would bring the strings closer to the fretboard. "Turning up" is a counterclockwise turn that would loosen the truss rod and would bring the strings away from the fretboard. Easy enough to understand.
How to adjust a vintage style Fender truss rod
This style of truss rod adjustment, be it on a vintage style Stratocaster, Telecaster, Jazzmaster, Jaguar, Precision Bass or Jazz Bass freaks people out because the neck has to come off in order to make a truss rod adjustment.
There's no reason to freak out, but I do admit it is a tedious process.
This is the process:
Step 1. Loosen the strings.
How much should you loosen? To the point where almost all tension is lost where the strings are about to come off the tuning posts. I'll explain why in a moment.
Step 2. Put a capo on the first fret.
You have to do this. If you don't, your strings are going to come right out of the nut and possibly scratch up your neck once you move it out of the neck pocket.
Step 3. (Assuming a 4-bolt neck plate) Loosen the two screws furthest away from the headstock almost all the way out.
By "almost" mean about 80% of the way out.
Step 4. (Assuming a 4-bolt neck plate) Loosen the two screws closest to the headstock between 1/3 and 1/2 of the way out.
These two screws don't need to come out as far. Just enough so we can do the "scary" part next.
Step 5. Tilt the neck out of the neck pocket.
This is the part that freaks people out, and it's best shown by example.
Here's an image of what it looks like:
Here is the video of where the image comes from. This is a Fender-produced video, by the way. Skip to 4:05 to see this process in action.
I don't totally agree with the way the tech took the neck out of the pocket. As stated above, I recommend loosening the strings and then putting a capo on the 1st fret. I also recommend loosening the screws more than what's shown in the video to provide more angle. What's shown may work for a Fender bass but I doubt it would provide enough tilt to fully expose the adjustment screw for adjustment on a 6-string guitar.
It's at this point where you realize why I said to loosen the strings. On a 6-string guitar, when you tilt the neck out of the pocket, if your strings are still at pitch you won't get enough tilt angle to get to the adjustment screw. When the strings are loosened, you do.
What I do agree with however is that you do not have to remove the strings nor the entire neck off the body just to make a relief adjustment. You can keep the strings on and the neck semi-installed in the pocket and still get the job done.
The thing to know about taking a neck out of the pocket for relief adjustment is that there really is no civilized way to do it. Once the screws are loosened, you do have to push to get that neck out of the pocket where "putting a little English on it" is required. The first time you do it, you will probably freak out a little because you are physically taking apart the guitar.
Step 6. Adjust relief.
Again, clockwise a.k.a. "turning right" will tighten the rod and bring the strings closer to the fretboard, and counterclockwise a.k.a. "turning left" will bring the strings away from the fretboard.
There is something stated in the video that I will echo here. There's no way to know if you have adjusted the relief correctly or not until you get the neck installed again and all strings tuned to pitch at which point you can test relief distance. This means yes, you will have to guess how much adjust.
Step 6a. How much should you turn?
The general advice is to give a 1/8 turn. A 1/4 turn is only necessary if you've got some major string buzz issues going on even with the string saddles set correctly, or if the strings sit really high off the fretboard even with properly set string saddles.
Obviously, you need to check the relief before you take off the neck.
Quick-and-dirty method to check relief: Tune your strings to pitch. Put a capo on the 1st fret. Hold the last fret with your picking hand. Tap the 6 string at the 12th fret. Listen for a tapping/clicking sound, and examine how much room there is between the string and the fret. If there is no tapping/clicking sound and the string is resting flush on the fret, the truss rod needs loosening to bring the strings away from the fretboard. If there is a ton of room, the truss rod needs tightening to bring the strings closer to the fretboard. Optimal spacing is generally considered to be about the thickness of a credit card or American quarter coin.
Step 7. Reattach the neck.
Step 8. Remove the capo and tighten strings to pitch.
Step 9. Wait.
I give the neck 24 hours to settle after making an adjustment before attempting another adjustment if need be.
Why do I do this? Because I have made the mistake before of making a truss rod adjustment, checking relief, adjusting again, being satisfied with the relief only to find it not set right when I check it the next day. In that instance, what happened is that the wood settled over the night and the relief changed slightly from where I had it set.
On a Fender neck with vintage style heel adjust for the truss rod, believe me, it is worth it to give the neck wood time to settle else you'll have to take the neck off again for another adjustment.
How often are truss rod adjustments necessary on a Fender maple neck?
If you don't bounce around with different string size sets, and neither the ambient temperature nor the RH (relative humidity) level changes drastically, you should not have to adjust the neck relief that often.
For those of you who gig, yes you will have to adjust neck relief more often. But if the guitar stays mainly at home, I seriously doubt you would have to adjust neck relief more than just a few times per year, if that.
Remember, hard maple is an excellent neck wood. Once you have the relief set to your liking, it will stay put and you shouldn't have to be constantly adjusting it.