Replacing a Fender USA Stratocaster Bi-Flex Truss Rod Nut

Comparing old and new truss rod nuts, old one is very worn.

For some reason known only to Fender, the US American Standard Stratocasters and Telecasters use a 1/8″ Allen key to adjust the Bi-Flex truss rod. It’s okay if the rod is working well and whoever adjusts it used a tight-fitting key of the correct size, but if not, the nut can quickly be trashed and require replacement.

Replacing the nut is not difficult but does, like every job, require a bit of care. It sits behind a walnut plug which has to be removed. The nut pushes against this plug if you use the truss rod to introduce bow into a neck.

The first step is to score the finish around the plug so that it isn’t damaged. I omitted to photograph this step.

Next the glue that holds the plug in has to be softened. I did this by placing the bit of a soldering iron into the hole. This required more heat than I expected and did cause a little charring of the plug but this is being replaced with a new one.  No pictures here either sorry!

Once the glue is soft, turning the truss rod nut anticlockwise will cause it to act against the plug and push it out.

Unwinding the nut pushes out the plug from inside

Withdrawing the walnut plug

Once it’s far enough out to grip, pliers can be used to pull it all the way out.

Walnut plug is out

Walnut plug is out

The nut can now be withdrawn using the 1/8″ Allen key.

Extracting the Fender Stratocaster truss rod nut

A bit of twist on the Allen key and out it comes

Once the nut is out it’s important to clean the sides of the hole so that the new plug will fit and the glue will adhere to the sides.

Here are the old and new nuts so you can see how chewed the hex socket was.

Comparing old and new truss rod nuts, old one is very worn.

Look how worn the old nut was

The new nut should be inserted and nipped up. I applied a smear of lithium grease to the threads and inner face before I refitted it.

I roughly shaped the new plug on my belt sander and tested it for fit.

Test fit of new Fender USA walnut plug

Should do nicely

Next job is to put the small washer back in and glue in the plug with a little Titebond.

Once the glue is dry the plug can be carefully sanded flush…

Walnut plug sanded flush

Looking tidy!

…then refinished to match the surrounding headstock.

The walnut plug and surrounding area are refinished

Can hardly tell it’s been out

The only thing left to do was to set the guitar up with the user’s chosen 9-42 strings. I think it’s the first time in a long while that the neck on this guitar was been straight!

Fender USA Stratocaster Deluxe

Fender USA Stratocaster Deluxe

19 Comments on “Replacing a Fender USA Stratocaster Bi-Flex Truss Rod Nut”

  1. Hi. What does the phrase “nipped up” mean? I’m about to fit a plug an not sure how much the new nut should be threaded on to the truss rod. Thanks!

  2. They used to, though. From 1982 to 1984 and from 1989 to 1995, U.S.-made Fender basses did have Bi-Flex truss rods. But since basses rarely need counterclockwise truss rod adjustment, more powerful single-action truss rods with a larger diameter replaced Bi-Flex truss rods in Fender basses.

  3. I know this is an older post. Looking for some advice. I just did this repair a few months ago. Nut was badly stripped when I bought the neck. Now I can’t seem to get the neck as straight as I would like, even with the rod very tight.. Did you put any back bow in the neck before replacing the plug? I feel like maybe that’s what needed to be done in my case. When I read Fenders explanation of the biflex rid, it apparently uses the plug as part of the mechanism. I have an extra plug if I need to repeat the process.

    • The truss rod nut acts against the plug to give back bow so you can’t introduce any before the plug is fitted.

      The problem is probably in the neck or rod and the nut was stripped trying to straighten the neck when it’s just not possible. Sorry.

  4. All very good but it all falls apart if the trussrod nut cannot be used to push out the plug. My method is basically the same as yours but prior to heating the plug I tap in a 1/4″ thread. once the glue is melted I quickly run a 1/4 rod into the plug and yank it out. Once the plug is removed the nut can be accessed but that is another issue all together.

  5. A quick point, if the hex socket is badly chewed up and you can’t get a hex wrench to grip try using a Torx bit, it will grip where the hex doesn’t (it’s also possible to gently tap in an oversize Torx bit into the damaged hex socket)

    • would this work on any other kind of biflex rod. EG I have a ‘Vintage’ (JHS brand) guitar and the thread has stripped on the nut. Could I remove the plug and chgange thenut in the same way.
      Cheers mart

      • “Biflex” is a Fender trademark and no other make of guitar uses this kind of truss rod (thankfully).

        The two-way truss rod in your Vintage is a totally different construction and the nut isn’t removable.

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