Luthier Tips du Jour Mailbag - Nut Slots

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In this episode, Robbie O’Brien answers a viewer’s question about how to fix a string buzz at the nut slot.

Video Transcription

[on-screen text reads: Luthier Tips du Jour Mailbag]

Mailbag question: I'm having some buzzing on my B string at the nut. I think the slot is too low. Is there anything I can do, or do I have to make a new nut?

Robert O'Brien: Today's Tips du Jour mailbag question comes to us from Argentina. "Dear Robert, I'm having some buzzing on my B string at the nut. I think the slot is too low. Is there anything I can do, or do I have to make a new nut? Manuel in Argentina."

Yes, Manuel, there is something that you can do without having to make a new nut. I use CA glue and baking soda or bone dust to fill the slot, re-slot it with the file and then put the string back in it. And it's a little bit higher than it was, therefore no buzzing. It's a very easy trick to do. Now, on a commissioned guitar that's leaving my shop for the first time, I probably wouldn't do this, I'd go ahead and make a new nut, but if you need a quick fix, this is the way to do it. And I'm told that the final product is harder than the bone itself.

Diagnose the problem

So let me show you how I do it. The first thing you need to do is diagnose that the string being too low in the slot of the nut is truly the problem. And I've got a guitar here that the G string is just a tad bit low. Now, if I play it normally, there's no problem. But once you start to overplay it and push it a little bit, then it's going to start to buzz. It's really borderline at this point, but why not go ahead and fix it?

Apply baking soda to the low slot

So the first thing I do is remove the string from the slot, and you don't need to detune it to do that. Next, I'm going to take a small amount of baking soda and apply it in the slot. Emphasis on the small amount. If you place your finger over it and then blow, the excess will go away, leaving the baking soda only in the slot.

Apply the CA glue

For the hardener, I'm going to use thin viscosity CA glue, and I'm going to be using a brand called Hot Stuff that I get from Satellite City. Now, to apply the glue, you don't want to get happy with the glue and have it run all over your fretboard and all over your nicely finished peghead. So I'm going to use a very small pipette. This allows me to strategically place the CA glue exactly where I need it.

So with the small pipette, I'm coming in and placing just a small drop right where the slot was. Once the glue is applied, allow it to dry. I'm not going to use accelerator. The reason why is perhaps the accelerator will react with the finish. I don't know. Also, the accelerator has a tendency to dry the glue a little bit too quickly for my taste, and you can get some heat buildup, and therefore, get some boiling of the CA glue. So I'm just going to let it dry, and it dries very, very quickly. Once it's dried, we can come in and re-slot the slot.

Re-slot the slot with a nut slotting file

So now that the glue is dried, I'm going to come in with my nut slotting file. Now, this is a specialty file for slotting the nuts. That's its only purpose in life. And for my strings, I need a 0.024" diameter file. And what do you know? I just happen to have one right here. What are the chances of that? [Robert files the slot down a little bit] Now, I like for the action of my strings to be in the neighborhood of 0.015" on this string. So I'm going to use this dial indicator to dial in the exact height of the string above the fret. Right now, I'm coming in at about 0.022", so I can take my nut file again and bring it right down where it needs to be [Robert files the slot some more with the nut file]. And I'm coming in right at around 0.015". So that's good. Let's see if it buzzes. Problem solved.

This is a brand new bleached bone that I've used for the nut here, so there's no discoloration. Now, if there were some browning or some antiquing of the nut, perhaps you would want to sand a little bit off of the nut itself to fill the gap instead of using baking soda. That way, your color match is perfect. But for this guitar, I'm good to go. So, Manuel in Argentina, I hope this information has been helpful, and I don't want to hear any more buzzing on that nut. Now you know how to fix it. And happy building.

[More Luthier Tips and online courses available at www.obrienguitars.com. Private and small group guitar building and finishing instructions available.]

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Robbie O'Brien

Luthier and Instructor, Lutherie Academy