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How to Adjust a Fender Truss Rod

I don’t believe I am obsessive regarding the relief and action of my guitars. But I do check my string height from time to time, particularly when I begin wondering if the reason those bar chords seem more difficult to play is that I am getting older (which of course I am) or because I need to make some adjustments. This happened last week on my Squier Classic Vibe 60s Thinline Telecaster. Because I keep records (I am a retired scientist and I can’t help recording notes of what I’ve done) I knew the last time I adjusted the relief on this guitar was 13 months ago.

4 mm Allen wrench for Squier Truss Rod Adjustment

The same day I planned on adjusting the relief on my telecaster I saw a new video on Truss Rod adjustment by Dan Erlewine from Stew-Mac. I’ll discuss his video later in the post. Although I’ve been adjusting the relief on my guitars for years, it’s always good to learn new tricks from professionals.

My first advice is to make sure you have the right tools for the job. Modern Fender and Squire truss rods adjust from the head, unlike vintage models which adjust at the heel of the neck. You need a hex key Allen wrench of the proper size to adjust the most recent modern Fender guitar necks. For years I used a standard L-shaped hex key from metric or SAE (American) Allen wrench sets. The problems with these are their sizes are unmarked, the metric and American sizes are mixed together, and inevitably I lose the size I need most. After years of adjusting the relief on my guitar necks, I’ve remedied this problem by purchasing a set of T-handle metric and American sized hex keys, color-coded as to whether they are metric (blue handles) or SAE (red handles) and with the sizes clearly marked on each of them.

T and L handle Allen hex wrenches. Fender has ball end.

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Metric and SAE Allen Wrench set from Amazon

Gibson and other brands of guitars, acoustic guitars and other instruments will have their own requirements for neck relief adjustment. Most of them use an acorn-shaped nut that requires a socket wrench to turn. You may be able to use these Allen wrenches on other guitars you own, but the only guitars in my collection that use these are from Fender or Squier.

If you only have one guitar that needs an Allen wrench, a set might seem like overkill. If you own a made-in-Mexico Player series Fender, the proper size Allen wrench is 3/16 inches. You can purchase a single Fender branded T-handle hex key for less than half the price of the combined set above. However, the size key for Squier guitars is 4 mm and the size for USA Fenders is 1/8 inch. Since I have a MIM Telecaster too, the set made sense. I will use these on non-guitar projects so it seemed a good deal for me.

Fender 3/16 inch Allen Wrench from Amazon for MIM Fender truss rods

Hex wrench sizes needed for Fender Guitars

Allen size size in mmsize in inchesGuitar
1/8 in2.7150.125Fender USA
4 mm4 mm0.1575Squier
3/16 in4.76250.1875MiM Fender

Should you get ball end Allen wrenches? Ball end keys do two things that can be helpful. First, they make it slightly easier to fit the key to the nut which is hidden on Fenders. The more important thing is the ball allows you to use the key at an angle when it isn’t perfectly in line with the nut and truss rod. The Fender Truss Rod Wrench has a ball end. The argument against having a ball end is you can’t put as much torque on the nut with the ball and the ball is a weak point more likely to fail when trying to turn a stuck nut. The set I bought and show above does not have ball ends but the single official Fender T-handle 3/16-inch Allen wrench has a ball end. As far as I can tell Fender does not sell any size of branded Allen wrench other than 3/16-inch and the only line of guitars 3/16-inch works on are the MIM guitars and basses.

Measuring Your Neck’s Relief

Checking the relief on your neck can be done by holding your guitar in the playing position, fretting the 6th string at the first fret and the 17th fret (or if not a Telecaster or Stratocaster, fretting at the fret where the neck joins the body). This is made easier if you put a capo at the first fret but I rarely use the capo for this. You then want to look at the distance between the bottom of the string and the top of the frets at the midpoint which is the 8th fret.

Fret at 1st and 17th frets and check at 8th by tapping, sight, or measurement

In general, I do not actually measure this distance although, I have attempted to do so out of curiosity and completeness. Feeler gauges can be used for this. If you want a ballpark estimate, I’ve seen the suggestions to use something between the thickness of a single piece of paper to that of a business card and see if it fits between the strings and the frets.

I use the tap method. I want some relief, but not much. Tap the string above the fret to get a feel for how close to the fret it is. If you can’t hear the string click against the fret, your neck is flat or has a back-bow (bad). If you can hear a slight click, you’re good. If you can feel the string move and hear a loud click, you probably have too much relief.

But, remember, this is partially a personal preference. Some people want more relief than others. 

For Fender’s official guide to measuring relief see this.

Steps to adjusting the relief on your Fender or Squier non-vintage neck.

3/16 Allen for MIM Telecaster Truss Rod

Please read ALL of the following before turning the Allen wrench in the truss rod nut. 

  1. Loosen the strings on your guitar. This removes the force pushing against the nut on a one-way action truss rod, which is what most guitars have. It will make the nut easier to turn.
  2. Fit the proper size Allen wrench into the nut. Do not put any pressure on the nut until you are sure the Allen wrench is the correct size and is firmly seated, otherwise you could strip the socket.
  3. Once the Allen wrench is seated, note the position of the T, or L handle. You want to make only small adjustments and need to know far you’ve turned the handle. In general 1/8 to 1/4 of a turn at a time is all you want. But, don’t turn that handle yet!
  4. If you have too much relief and need to flatten the bow on your neck, watch the following Dan Erlewine video below first. The gist of the video is to intentionally force the neck into a slight back bow first. This reduces to force and makes the nut easier to turn. I’ve skipped this part but it seems like a good idea. Clockwise (righty-tighty) tightens the nut and forces the neck to counteract the force of the strings.
  5. After making an adjustment, tune back to pitch and check the relief again.

Dan Erlewine 

Another recommendation: Turn the truss rod a quarter-turn counterclockwise first to loosen before beginning to tighten the nut. This ensures that the nut hasn’t rusted onto the truss rod and is able to turn freely. 

If you can’t turn the nut or have other problems making an adjustment, take your guitar to an expert. I have never broken a truss rod, but others have.

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