General tech questions

How to file a nut?


I'm changing a guitar from right to left handed. I got a new nut for it but it needs to be filed. Since I have decided to learn how to do some work myself I ordered a set of files. Cheap ones but I figure good enough for now. They should be here later this week. Any advice would be great. What to do, what not to do and such.



Tip #1: Don't use drunk thread to file with


The most difficult part is the string spacing, if you don't have a spacing ruler. As far as the nut itself... I get mine to a workable size on the bandsaw & rough it out on the belt sander. From there I glue it in & cut the string slots. You can use the original nut for reference for spacing. once I get the string depth where I want it & I file the top down to height. Buy a couple blanks so you have one to screw up. If you don't, you'll have another for next time ;-)


Thanks! I have it marked and the size is good so I guess I'll go ahead and glue it in place and wait for my files. I have a spare brass nut that I was saving for my 5120, I guess that can be my backup in case I screw up the first one. I have a set of old strings to put on the guitar to help me determine slot depth.


When start to cut the string slots, go slow. Keep checking the height to the first fret. Take your time. You don't want to cut them to deep.


UG, don't glue it 'till you're happy with it. Triple check your string width measurements then put it in place and start cutting. Keep the strings on the neck and just loosen them up enough so they'll pop out of the nut. Mark a rough depth above the final depth, add string from time to time and eyeball in relation to the first fret. Keep doing that until you have it where you want it and glue it in place.

Measuring the depth won't get you to where you need to be, use your eyes and fingers to determine that.


Curt, thanks! You just made me feel smart. I was planning on keeping the strings on and using the distance from string to fret as my ruler. Groovy.


Tip #1: Don't use drunk thread to file with

– Geoff_Vane

Tip #1: Don't use drunk thread to file with

– Geoff Vane

No fun, but wise words.


I recall reading somewhere, perhaps on the fret-not site, that the nut slots should be filed with a bit of a ramp with the highest point towards the bridge and the lower side towards the tuners.


Hermitt, you are correct. I always file towards the tuners in sort of a downward stroke to get the angle. My ES-175 nut(it's a factory nut)is cut on an extreme angle where the strings sit in the nut almost as if they were in a bridge saddle. I guess everyone has a style of cutting a nut. I also like to run the file towards the tuning machine to get the string headed in the right direction, to give the string one less place to hang up. It all takes a little practice, but it isn't terribly difficult.


I was thinking straight line from nut to hole in post.


The most difficult part is the string spacing, if you don't have a spacing ruler.

You can print the nut spacing template available from here. Makes the layout of a new nut a breeze.

For the rest of the process, there's a really good how-to guide over at Stew Mac.


You can start the nut slot with an X-Acto knife or thin Japanese saw. This is best because the slot files will chatter a bit. Once the slot is started with the X-Acto or saw, the files work easily.

I usually go one size up from the size of the string, so there is no binding. Once you have the depth where you want it, lube the slot with pencil graphite or Chapstick.


You can start the nut slot with an X-Acto knife or thin Japanese saw.

Good call. I've got a model maker's tenon saw which is perfect for this sort of thing and, from memory, was less than £3.


If you don't know the "half pencil" trick, you need to :D


Thanks guys. Got the files today. They are CHEAP. But they'll do. I have the basic slots cut and filed. I have them filed about half way so far. I'll glue the nut down now so I can file to depth. If this works I'll be very happy. It's a lot more fun than having someone else do it.


I was thinking straight line from nut to hole in post.

Not a good idea. You never want the string to make a sharp angle.
You have to take care that the string makes a nice curve, entering the nut at a straight angle and leaving the nut at a straight angle towards the tuning peg. And in between should be a nice curve.
Start cutting the slots straight from the fret board side. And then when you have the right spacing start filing the slot in a curve towards the tuning peg. Do it with a smooth rotating motion, angling the file in the right direction and down towards the back. The front of the slot has to be the right height and the slot should aim down slightly in a nice curve.

You want the string slot to be nice and round to fit the shape of the string exactly. The trouble is that the files never are exactly rounded. Specially cheap ones. But that doesn't matter. If you file with a rolling motion the slot will become round. And that way you can also shape the width of the slot by feel. You can make it wider by rolling the file some more.
Always keep the slots very slightly higher than they'll need to be. They always sag a tiny bit after a day or so. And you can always go lower the next day but you can't go back.......
After the filing you have to make the slot smooth. There are several ways. Nowadays I use the Stewmac abrasive cord but in the past I have also used very fine sand paper wrapped around a guitar string. Play around with that and find a width that will be good for the slot.
After making the slot nice and rounded and smooth I polish the slot with polish and dental floss. If you look at a slot with a magnifying glass that was cut with a file you'll see that it is rough. If you sand it nicely and then polish it you'll see that it is very smooth. That's what you want.
Of course you also have to shape the nut itself after you have the slots cut to the right height. And you can sand and polish it to make it looking nice and shiny.


Btw: When filing the slots to the right depth I have the guitar strung to pitch (and the truss rod at the right tension) and I am constantly lifting out the string of the slot I am working on. Then I put it back in, check and lift it out and file some more. Until it is the right height.

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