Photo 1

Recently a client brought a fairly new American Fender Strat into the shop. The neck had too much relief, but otherwise the guitar was in great shape. No problem, I thought. Tighten up the truss rod a bit and we’ll be good to go.

I unwrapped a new Fender hex key (more about the condition of your tools in a moment) and inserted it into the truss rod nut. But instead of finding a secure grip, I felt the tool spin around inside the nut. Oh, that sinking feeling: I realized the nut’s socket was stripped, which is very bad news for this particular Strat.

Why? The truss rod nut on this type of Strat is recessed into the neck and surrounded by wood (Photo 1), so when the socket that holds the truss rod tool is stripped out, you only have two options: perform major surgery to remove the stripped nut and replace it with a new one, or buy a replacement neck. Realistically, it would cost more to perform the extraction, so I advised my client to contact Fender about getting a new neck.

Fortunately, not all Fender guitars have a recessed truss rod nut—in fact, many guitars don’t. You can often replace a stripped truss rod nut, and it’s not a tricky repair if you know what you’re doing. Inexpensive replacement nuts are available from such suppliers as Stewart-MacDonald, Luthiers Mercantile, and Allparts.

Different types of truss rod nuts. Before we discuss why a truss rod nut might fail and how to fix it, let’s explore several common types of nuts used on guitars. You adjust some nuts by inserting a tool into them, others by enclosing them with a nut driver or special socket wrench.

Using the wrong tool to adjust a nut is the most common cause
of truss rod problems.

The nut placement varies too: On Taylor and Gibson instruments, for example, the truss rod nut is typically located at the headstock, under a plastic or wood cover. These are among the easiest to remove. Some Fender guitars have a “bullet” truss rod nut at the headstock; these are not recessed and can be removed without surgery. Older Fender guitars have a truss rod nut at the heel of the fretboard, and these are very easy to remove, once you take off the neck. Some modern electrics have an exposed “wheel” nut located at the heel, and these can be adjusted without removing the neck.

Some acoustics, such as Takamine and modern Martins, have a truss rod nut that you access through the soundhole by inserting the tool through a small hole in the upper top brace (located between the soundhole and neck block). In some cases, this hole is just big enough for a wrench to poke through, but not big enough to accommodate the nut. The brace can be removed, but that is considered a surgical procedure, which is why some luthiers opt to simply enlarge the hole to remove the nut.

Truss rod tools vary, as well. Some require a hex key (Allen wrench), while others take a flathead or Philips screwdriver, a nut driver, a mini socket wrench, or a small metal rod. To learn more, read “Demystifying Truss-Rod Tools.”

Why truss rod nuts fail. There are three main reasons why you might have a problem with a truss rod nut.

(1) Hardware defect.

(2) The wrong size tool was used in an attempted adjustment.

(3) The correct tool was used, but it was worn.

A manufacturing defect is pretty rare, but they happen. When you think about how many guitars are built (probably millions each year), there’s a good chance a few lemons are going to squeeze through. It usually comes down to poor quality metal or slight discrepancies in manufacturing tolerances.

Photo 2

Using the wrong tool to adjust a nut is the most common cause of truss rod problems. I’ve seen many nuts that were ruined because someone decided to force the wrong tool around or into them. Photo 2 shows a Fender bullet nut that suffered this fate. Once a socket’s edges have been rounded like this, the hex key can’t grip the nut to turn it.