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Do you ever get frustrated trying to find the correct wrench or hex key to adjust your guitar’s truss rod? Well, you’re not alone! I have at least 20 different wrenches and hex keys dedicated to adjusting guitar necks (Photo 1), but I still run across that one guitar that requires a tool I don’t have. There are so many different tools designed for adjusting truss rods that it’s nearly impossible to have them all.
Many manufacturers include a truss rod tool when you buy one of their guitars. However, not all do, so you may need to purchase the appropriate tool. This is also true if you buy a used guitar missing its original tool.
Sometimes you can buy the correct tool at a home improvement store, but often you need to acquire it directly from the manufacturer, or from a luthier supply shop like Allparts Music, Stewart-MacDonald, Luthiers Mercantile, or the Luthier Tools page on the Martin Guitar website.
But before you go hunting, take a moment to acquaint yourself with some possible tools and how they’re used. Your truss rod’s nut type determines the tool you’ll need. It may be a hex key, nut driver, screwdriver, box wrench, or miniature screwdriver. Let’s look at each category.
Hex key. Some manufacturers, including Larrivée and Collings, use a long, bent hex key to adjust the truss rod. These builders don’t drill a hole through the cross strut brace (glued under the top between the soundhole and neck block), and the curved key lets you reach around the brace to engage the truss rod located in the neck block (Photo 2).
Other brands, such as Martin and Ovation, use a long hex key bent at a 90-degree angle. Takamine, Alvarez, Hamer, and modern Fenders use short 90-degree hex keys. The access point for some of these guitars is located inside the soundhole, while others adjust at the headstock. Like Martin, Takamine drills a small hole through the cross strut brace to provide soundhole access to the truss rod nut using a right-angle tool. The size of the hex key varies from brand to brand, with some as small as 1/8" and others as big as 5 mm.
Some instruments, including certain G’Zan models, have a side adjustment nut (Photo 3). This allows you to adjust the truss rod nut from the treble side of the heel—very convenient!
Remember, the guitar may need either a standard or a metric hex key, so check with the manufacturer to determine the right size. A snug fit is important for complete control over the amount of force needed to make an adjustment.