Nut Slotting Files

Looking at the nut of your Fender Strat, Gibson Les Paul, or any acoustic guitar, you will see that the strings fit into small notches or slot in the nut. These slots vary in size both in width and depth to correspond with their strings. Nut slots not only control the string spacing, they also control the action or height of the strings above the lower frets. Needless to say, nut slots are important. The only traditional file that could approximate these nut slots is a small triangular file. Unfortunately, most triangular files are too wide to make nut slots. In order to get the proper depth of the nut slot you need a narrow, pointed file that can file deep enough into the nut without making a wide slot. That is why nut slot files were invented.

How it works

A nut slot file is a narrow double-edged file. These files come in sizes that correspond with common string sizes. Each side of a nut slot file is a different size, so you only need three different sizes of nut slot files for all six strings.

After you have made your nut and laid out the string spacing, you are ready to file the slots with your file. Take your nut slot file and file toward the headstock. This is known as back filing. You want to keep the angle of your nut slots the same angle as the headstock. If you cut flat slots in your nut, your guitar will sound like a sitar because the strings will buzz in the flat slots. An angle ensures the string is only touching one point of the nut. Be very careful not to file into the headstock. You might even want to lay a piece of plastic or wood down, so you don't accidentally file into it. Also, never file toward the fretboard. It is difficult to achieve the proper angle of nut slot filing this way. You are also very susceptible to damaging the fretboard. Look at the sizes on the fret files and match them up with the string sizes. Here are the usual nut slot file sizes for each string.

Needless to say, a nut slot file is a necessity. You can't even make a nut without a proper set of nut slot files. You might be thinking, "Well they sell pre-slotted nut. I'll just buy one of those." The problem with that is most of the pre-slotted nuts still need minor adjustments to their nut slots. You will still need a set of nut slot files. These are a must have for every luthier or guitar repairman. If you would like more information about how to use nut slotting files, please see my how to adjust action at the nut article.