Official Luthiers Forum!

I've never seen a discussion in all my years here on how to properly adjust a truss rod so I wanted to create a thread that could be accessible to others and help folks out.

First is how do you evaluate the truss rod and neck to make any adjustments.

It's two sightings with the instrument on the bench, tuned to pitch (the tuning that the player uses because tension matters) and then lifting the head stock up I sight down the treble edge of the fret ends and fret board and separately the bass side looking for the same things.

Ideally we want the treble side to have less relief than the bass side and the best builders build this into their instruments which may be news to some here, not all. If you wonder how it's possible to have two sides of the same neck react differently with only one truss rod it's entirely possible if you mill in proper relief to your fret work when you build the thing.

So I want to tighten the rod (clockwise turns never more than 1/4 turn at a time) until my treble side is nearly flat. I adjust for very little relief for concert pitch tuned instruments. Now if the bass side has more relief built in I'm done. But 50% of the time (because what your neck looks like is luck of the draw from the stinkin f*ctories except Collings and a few others) If the bass side has less relief I have to leave some relief on the bass side and now have too much on the treble side.

So what do you set your relief to? Don't know what you set your's to but if I have less relief on the treble side I might only adjust for .002 - .003" of relief on the treble side, nearly flat but not flat.

You can use the string tuned to pitch to check relief fretting and holding in various locations the string is actually nearly... nearly a straight edge except for gravity.

Slack tunings and you need more relief. Slide player and the action is way high so it doesn't matter as much.

Moving on. This was adjusting now it's time to talk about why truss rods matter.

Nearly every couple of days we can save a guitar from the trash heap because it has a truss rod. Almost as frequently we can save a guitar because it has a double action truss rod.

Moron of the story other than being me is - use a truss rod and use a double action, quality rod. If the rod fails you are in deep doo doo and the repair could be very pricey....

Now let's have your questions about truss rods and anything else that someone wants to contribute.

Question of the day is what is different about a Rickenbacker's truss rod?

I’ve built a lot of guitars using a two-way rod. I have to crank the heck out of them to adjust the neck.
I had an early LP with the single curved rod. It was very responsive to rod adjustments.
My necks are never flat when the rod is loose. Any tips to fix this would be swell.
I use a flat caul against the fretboard, and I glue it before radius.
Question: it it safe to assume the rod will bend exactly in the middle?

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Wah-wah-wah-wah
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Rickenbackers have a double truss rod, which is removeable from the peghead end.... I've done it. Personally, I think double truss rods are a good idea on 5 & 6 string basses, and any guitars with more than 6 strings.

Also, Ricks require a special wrench to adjust them - which I bought from the factory back in the early 80's when my main bass was a Rick.

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"Act your age, not your shoe size" - Prince

not all 2 way truss rods are the same. The ones with the end silver soldered or brazed on I had used failed and never will use them again. The martin style are very reliable . A truss rod will held with relief but if your frets are not perfect you won't get the best out of the guitar so also be sure frets are level and true.
it is worth the effort

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I too have settled down on using the Martin style two way rods and agree that a two way rod is superior in most cased. Those old Gibson rods do work well though and a little bit goes a long way.

The only thing I would add is that as a builder I like to make it so that the truss rod is removable. I still have to remove my bolt on butt joint neck to do it but still it's just one more assurance against trashing a neck that has a broken rod in.

I imagine most of us here not only sight the necks like aiming a rifle but also use the string as a straight edge to measure relief?

as a machinist I have parallels and straight edges for measuring relief , I also found planer blades make great straight edges

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

I had an interesting issue with the last guitar I built. It is an archtop with a floating neck over the body. I wanted that nice and stiff so I followed Bob Benedetto's advice and put two square carbon fiber bar next to the (double acting) LMII truss rod. I was very careful to build the neck dead flat, as are the frets. Under the tension of light gauge acoustic strings I only get 2 or 3 thousands of relief, which works but barely. Maybe its possible to build a neck too stiff.....

On banjos, with considerably less tension on the neck, for years I've used carbon fiber reinforcements with no truss rod. I've still not heard of any problems on these necks. What I did for neck relief was to backbow the neck by a little more than the amount of relief I wanted in a jig, and then flatten the fingerboard. Then, I'd engrave the pearl inlays and fret the neck. The slight amount of forward bow that would be introduced by the frets took the relief down to where I wanted it to be. With no adjustable neck, it relies a lot on really stable neck wood, but I've been successful with this method for a long time with banjos. I guess maybe I've been lucky about choosing good neck wood, and then laminating it to make pretty stable necks. Banjos made "in the day" of the style I build had no reinforcement outside of lamination anyway.

This process wouldn't work well on guitars, being under higher tension but the same basic idea might still be useful. On guitars, I've done sort of the same thing using two way truss rods by introducing a slight backwards bow before flattening the fingerboard, then proceeding like I would with banjos. Not nearly as good a method as Hesh's, measuring everything under tension. But it does get things into the ballpark at any rate. With the adjustable rod, final tweaking is still ready to go.

Dave

Exactly!!

Should we ask them what is different about a Rik 12 string's nut slots ?

OK here's another truss rod related tip. For US Fender the adjustor is way too shallow. If you use a ball end it can strip and if you use a non-ball end it can break off in the adjustor and frequently does. So when you encounter a US made Fender and the truss rod is near it's limit be sure your truss rod wrench is not a ball end and fits snug and is of quality steel or you may leave the tip in the guitar forever more.....

Can if you want. I already know the answer, because one of the first stores I ever worked at was a Rick dealer.

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"Act your age, not your shoe size" - Prince

It absolutely is, one example: I see old, student-grade archtops from the 40s with huge baseball bat necks and no rod, maybe a steel bar as reinforcement. Now the current owner wants to string em with 9s, instead of the flatwound 12s they were designed for. Relief has to be milled in manually and seasonal adjustments are not practical.

Necks don’t need to be hugely stiff, they just need to be stiff enough to, in combination with the installed truss rod, achieve the appropriate relief for a good setup. A nice bit of wood and a working rod is all that’s needed for your average six-string.

Great idea on the removable rod. Had a basically brand-new small-builder guitar in the shop a few weeks ago - DA rod adjuster was stripped - if it had been removable it would have saved the owner (and builder) much hassle shipping it back where it came from for a warranty fix.

And hey if we’re talking about how to adjust a rod, I like to give the rod a “helping hand” by applying pressure to the neck in the appropriate direction before tightening the rod. Also when an unfamiliar guitar lands on my bench I tend to loosen the rod a little before tightening it for the first time. Not sure if these are helpful rituals or just superstition but they feel like cheap insurance against broken rods or stopped nuts to me.

One thing I like to do too which is probably not necessary but I have it stuck in my head. Is if tightening the rod then I like to go a bit further then required and come back. What I envision is built in twisting pressure on the rod and coming back relieves that.