Nuts

Turnaround

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May 6, 2004
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Independent Instrument Technician - Retired
Let's start by looking at the function of the nut (a.k.a. top nut or string nut). It has three functions:

1. To act as a terminus at one end of the vibrating part of the string
2. To set the spacing of the strings at the headstock end of the neck
3. To set the string height above the frets at the headstock end of the neck.

An exception to this list is found in the use of a zero fret, where the string vibration termination and string height are set by the fret and the nut is only used to set the string spacing. But let's ignore the zero-fret configuration for now.

To do those three functions well, the geometry of the nut needs to be just right. The material the nut is made from also affects its performance. Let's start by briefly looking at the nut material.

Typically nuts are fashioned from bone, synthetic bone, plastic or a metal such as brass or aluminum, or wood. Though each may have its own sonic quality, that characteristic is by and large only noticeable when playing an open string. The damping effect of the fretting finger on the string on the section of the fretted string toward the headstock will remove most of the string energy that would make its way to the nut. And if the nut receives no energy its sonic quality is irrelevant.

Then there is the effect of the mass of the nut. Brass will have a higher mass than bone of the same size. And the differences in mass will have an effect on how the neck vibrates from string energy. The effect is small, very small, but some believe that they can hear the difference.

Perhaps the most important consideration of the material used for the nut is its resistance to wear. As you tune a string you are dragging the metallic wire under tension through a nut slot that has very little surface area. Then you subject that small surface area to vibrations under tension. So it is important that whatever material is used it will stand up to that stress. To that end soft plastics are not the best choice, and though metals may seem to be advantageous, they do not necessarily stand up to abrasion as well some other materials.

When it comes to the functions of the nut, the first and most obvious is that of being a termination point at one end of the vibrating string. For the string to vibrate it needs to have two fixed end points, and the tuner post cannot provide an accurate enough termination point, neither in terms of string vibration length nor string height. The nut provides a specifically located termination point, but only if it is cut well. I'll get into that a bit later, but for now let's look at the location of this "termination point".

One way to look at the nut is as the start of the fretwork. The frets are spaced along the fretboard at specific spots that will yield the notes we want. And there is a mathematical progression to their spacing. The position of the nut in relation to those frets is determined by that mathematical progression. Or viewing it another way, the position of the nut in relation to the bridge determines exactly where the frets are placed. Without making any other changes, if you were to relocate the nut nothing would play in tune other than the open string (assuming you tuned the open string).

But it's not just the location of the nut that is important for tuning. How the nut slots are cut is very important. A diagram will illustrate the point.

upload_2021-6-1_9-53-1.png


The distance from the nut to the first fret is critical. But the nut has thickness - distance B is greater than distance A, so it is important that the vibration termination point is precisely established a specific point in the thickness of the nut. Typically the nut is placed so that the termination point is on the fretting side of the nut rather than the headstock side. But to make sure that the "witness point" (termination point) is there the nut slot needs to be cut right. Looking at it from the side of the neck, in cross section:

upload_2021-6-1_10-7-57.png

Here the string angles down toward the headstock. The string's vibration termination point is at A, the critical distance from the first fret. The nut slot is angled down toward the headstock to ensure that the point A is well-defined. If the nut were reversed, the witness point would be at B which is too far from the first fret:

upload_2021-6-1_10-17-42.png


If the nut slot is not angled at all, not only is the termination point vague, but the string will have a tendency to rattle in the slot. So angling the nut slot down toward the headstock is important in establishing the right position for the termination point of the string's vibration.

The next post will deal with the function of string spacing at the nut.
 

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The second function of the nut is to space the strings correctly at the headstock end of the fretboard. Two measurements are of importance here, the distance from the edge of the fretboard to the string and the distance between strings.

Typically the outer edge of the string is positioned about 1/8" from the edge of the fretboard. Any less than that risks breaking off the outer corner of the nut. And if the string is too close to the edge of the fretboard it may tend to slip off the end of the fret while playing.

The space between those outer strings is divided either evenly or proportionally. There are advocates of both layouts, though proportional spacing is more common. In even spacing, the distance between the centrelines of the strings is constant. In proportional spacing, the distance between the outer edges of the strings is constant. Like this:

upload_2021-6-1_12-19-45.png


The upper nut has string spacing based on the centreline of each string (equal spacing) while the lower is based on the distance between sting edges (proportional). The difference is so slight to be of no importance to some players while others have definite preferences.

In the next post I will address the third function of the nut - setting the string height over the frets at the headstock end of the fretboard.
 
Probably the single most important function of the nut is to set the string height at the headstock end of the neck. Not only does it affect the ease of fretting on the lower frets, it also plays a very important role in the intonation of the notes on the first few frets.

Unfortunately, most often the height is set wrong. It is not a matter of personal preference the way overall string height is - there is only one nut height for any given bass and setup that is correct, anything else is at best a compromise. Keep in mind when I say "nut height" I actually mean the height of the nut's string slot that provides clearance over the first fret. Let me explain why I say there is only one correct nut height.

First consider what happens when you fret a note - let's say at the first fret. The nut is no longer part of the geometry of the vibrating string. The string path is from the top of the first fret to the bridge. The nut has no effect on that. First let's assume you would like notes to play cleanly (no fret buzz). If you have adjusted your bass well, between the neck relief and the string height at the bridge you will have achieved just the right amount of clearance between the string and the second fret to play cleanly. If you now play the open string, ideally it would behave the same way - the same clarity. That will only be achieved if the nut height is high enough. If it's too low there will be fret buzz when playing the open string.

Many players like to get a bit of fret buzz if they dig in to get a more "growly" tone. And once again, let's assume that your bass is set up so you get just the right amount of buzz when you dig in when fretting all up and down the neck. It would be nice to get the same response on the open string. Fortunately, it is easy to determine exactly what nut height will provide that arrangement. Simply fret at the first fret and measure the gap between the string and the second fret. That's the amount of clearance you need between the open string and the first fret. If you have less than that amount of clearance the open string will buzz more than fretted strings. If you have more than that amount you will have to dig in harder to get that amount of buzz on the open string.

You can also look at the way fretting feels at the first fret. If the nut is too high, fretting at he first fret will require more pressure than doing so at the 2nd or 3rd fret. And if it's too low you will need to play more gently on the open string to avoid buzz. It is a matter of consistency.

And it's a matter of intonation. With a nut that is too high that extra force it takes to play at the first fret will drive the note slightly sharp. Sufficiently high it may affect the intonation at the second fret as well.

Logically, the height of the nut slots will actually be the height of the frets. Then the string height is consistent fret-to-fret-to-nut. And some basses simply use a zero fret to achieve this. That takes nut height out of the equation since the nut will only be used to set the string-to-string spacing - the zero fret sets the height and the vibration termination point.

Getting the nut slots to this ideal height takes some care. You must make sure that the witness point is set at the nut before taking measurements. If not the string will show more clearance at the first fret because of the arc the string is forming over the nut. Please read the thread in this forum about witness points if you are unclear about this aspect of setup. It is very important and often overlooked.

The interesting part of this is that most of the guidelines for setting nut height recommend a setting that is too high. Even from respected techs and luthiers I see a recommendation of about .020" as the amount of clearance from string to first fret. That is about twice as much as any of my bases (.010"), all of which are set with moderately low action. My open strings behave just as my fretted ones. I can, however, see the advisability of adding maybe .002" extra height to allow for some nut wear. But after 20 years of gigging with my Number One, I have yet to wear the bone nut enough to require any adjustment. It also may be advantageous to incorporate that littke bit extra height to help prevent "back buzz", that sympathetic vibration of the string between the fretted position and the nut - a bit more clearance may help with that, but is more of a bandaid. And it doesn't matter if you are using small mandolin frets or super jumbos, the clearance over the first fret is the key and it should match the clearance over the second when fretting the first with maybe a tiny bit more height.

Low action requires attention to detail, precision fretwork and a precision nut. It's a game of thousandth's of an inch, and nowhere is it more evident that at the nut.
 
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Probably the single most important function of the nut is to set the string height at the headstock end of the neck. Not only does it affect the ease of fretting on the lower frets, it also plays a very important role in the intonation of the notes on the first few frets.

Unfortunately, most often the height is set wrong. It is not a matter of personal preference the way overall string height is - there is only one nut height for any given bass and setup that is correct, anything else is at best a compromise. Keep in mind when I say "nut height" I actually mean the height of the nut's string slot that provides clearance over the first fret. Let me explain why I say there is only one correct nut height.

First consider what happens when you fret a note - let's say at the first fret. The nut is no longer part of the geometry of the vibrating string. The string path is from the top of the first fret to the bridge. The nut has no effect on that. First let's assume you would like notes to play cleanly (no fret buzz). If you have adjusted your bass well, between the neck relief and the string height at the bridge you will have achieved just the right amount of clearance between the string and the second fret to play cleanly. If you now play the open string, ideally it would behave the same way - the same clarity. That will only be achieved if the nut height is high enough. If it's too low there will be fret buzz when playing the open string.

Many players like to get a bit of fret buzz if they dig in to get a more "growly" tone. And once again, let's assume that your bass is set up so you get just the right amount of buzz when you dig in when fretting all up and down the neck. It would be nice to get the same response on the open string. Fortunately, it is easy to determine exactly what nut height will provide that arrangement. Simply fret at the first fret and measure the gap between the string and the second fret. That's the amount of clearance you need between the open string and the first fret. If you have less than that amount of clearance the open string will buzz more than fretted strings. If you have more than that amount you will have to dig in harder to get that amount of buzz on the open string.

You can also look at the way fretting feels at the first fret. If the nut is too high, fretting at he first fret will require more pressure than doing so at the 2nd or 3rd fret. And if it's too low you will need to play more gently on the open string to avoid buzz. It is a matter of consistency.

And it's a matter of intonation. With a nut that is too high that extra force it takes to play at the first fret will drive the note slightly sharp. Sufficiently high it may affect the intonation at the second fret as well.

Logically, the height of the nut slots will actually be the height of the frets. Then the string height is consistent fret-to-fret-to-nut. And some basses simply use a zero fret to achieve this. That takes nut height out of the equation since the nut will only be used to set the string-to-string spacing - the zero fret sets the height and the vibration termination point.

Getting the nut slots to this ideal height takes some care. You must make sure that the witness point is set at the nut before taking measurements. If not the string will show more clearance at the first fret because of the arc the string is forming over the nut. Please read the thread in this forum about witness points if you are unclear about this aspect of setup. It is very important and often overlooked.

The interesting part of this is that most of the guidelines for setting nut height recommend a setting that is too high. Even from respected techs and luthiers I see a recommendation of about .020" as the amount of clearance from string to first fret. That is about twice as much as any of my bases (.010"), all of which are set with moderately low action. My open strings behave just as my fretted ones. I can, however, see the advisability of adding maybe .002" extra height to allow for some nut wear. But after 20 years of gigging with my Number One, I have yet to wear the bone nut enough to require any adjustment. It also may be advantageous to incorporate that littke bit extra height to help prevent "back buzz", that sympathetic vibration of the string between the fretted position and the nut - a bit more clearance may help with that, but is more of a bandaid. And it doesn't matter if you are using small mandolin frets or super jumbos, the clearance over the first fret is the key and it should match the clearance over the second when fretting the first with maybe a tiny bit more height.

Low action requires attention to detail, precision fretwork and a precision nut. It's a game of thousandth's of an inch, and nowhere is it more evident that at the nut.
concerning buzz at the nut, I have a brass nut on a spector euro bass. I had the bass setup with the direction to the tech that it needs to fit up to a 50-120 gauge 4 string set. I can't remember if the nut had to by physically altered in width and/or depth to accommodate, or if it worked with the stock nut. But it doesn't have any noticeable buzz or issues when tuned in D standard down to BEAD unless I really dig in. I'm looking to sell this bass and the seller asked if he returned it to stock EADG tuning with regular string gauges 45-105 if there will be buzz issues with the nut specifically. He understands the neck and saddles will need re-setup for that tuning and string size, but asked if buzz would happen at the nut itself. Any advice here? I don't know if it will effect it or not or if the nut will need replaced. Thanks
 
If the nut height is fine now and there is a good break angle, the existing nut slots will likely be fine with the change to a lighter gauge string.
 
<Snip>

Getting the nut slots to this ideal height takes some care. You must make sure that the witness point is set at the nut before taking measurements. If not the string will show more clearance at the first fret because of the arc the string is forming over the nut. Please read the thread in this forum about witness points if you are unclear about this aspect of setup. It is very important and often overlooked.

The interesting part of this is that most of the guidelines for setting nut height recommend a setting that is too high. Even from respected techs and luthiers I see a recommendation of about .020" as the amount of clearance from string to first fret. That is about twice as much as any of my bases (.010"), all of which are set with moderately low action. My open strings behave just as my fretted ones. I can, however, see the advisability of adding maybe .002" extra height to allow for some nut wear. But after 20 years of gigging with my Number One, I have yet to wear the bone nut enough to require any adjustment. It also may be advantageous to incorporate that littke bit extra height to help prevent "back buzz", that sympathetic vibration of the string between the fretted position and the nut - a bit more clearance may help with that, but is more of a bandaid. And it doesn't matter if you are using small mandolin frets or super jumbos, the clearance over the first fret is the key and it should match the clearance over the second when fretting the first with maybe a tiny bit more height.

Low action requires attention to detail, precision fretwork and a precision nut. It's a game of thousandth's of an inch, and nowhere is it more evident that at the nut.

What are your thoughts on fretless nut setup?
 
What are your thoughts on fretless nut setup?
The string should not touch the fingerboard at the nut. But it only needs enough clearance not to buzz. 10 thousandths of an inch at the nut between string and fingerboard is about what I use on my fretless basses, including my double bass.
 
I recently picked up an awesome Squier Matt Freeman P bass. I believe the stock strings are still on it. I'd like to go to a heavier set that fits my technique and tuning better. The bass spec came with .045-.105 which is what I assume is still on it, but I'd like to go to .050-.110 or .050-.115. Will either of these work with the stock nut slots or would both require a file? Or use a snip of the string to file it since I don't own files. Thanks
 
Most often you can go up a gauge or two on a factory cut nut without a problem. Try your choice in the nut slot - it should seat to the bottom of the slot without gaps and it should slide back and forth without binding. If you need to widen the slot a bit you can use the original string and wrap it in a piece of fine sandpaper to widen the slot. Or a piece of sandpaper wrapped around a drill bit of appropriate size.
 
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Most often you can go up a gauge or two on a factory cut nut without a problem. Try your choice in the nut slot - it should seat to the bottom of the slot without gaps and it should slide back and forth without binding. If you need to widen the slot a bit you can use the original string and wrap it in a piece of fine sandpaper to widen the slot. Or a piece of sandpaper wrapped around a drill bit of appropriate size.
thanks, it's a synthetic bone nut. does this process still apply?
 
It's very interesting to read professional's posts about different aspects of bass setup! As I understand, optimal nut height has straight relation to a given bass fretwork and action setup - neck relief and string height at the bridge. If the frets wears out or we have changed action setup or neck changed relief due to air conditions, nut's height is not optimal anymore?
 
Changing relief is necessary when there is not enough string clearance when fretting the first few frets. Adding more relief will increase the distance between string and frets in that area of the neck, including the distance between the string and first fret. So no change is needed at the nut. The change at the first fret will be proportional to the change at the second. Same with raising the bridge. If the nut height was optimum before the change of relief or bridge height, it will be optimum after the change.

In the simplest of terms, the bottom of the slot in the nut should be at the same height from the fretboard as the top of the fret is to the board. The nut is really just another fret that does double duty as a string spacer. We may add a couple of thousandths to the nut height to accommodate a bit of wear over time.

If the frets are worn or dressed the nut will no longer be optimum.
 
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In the simplest of terms, the bottom of the slot in the nut should be at the same height from the fretboard as the top of the fret is to the board. The nut is really just another fret that does double duty as a string spacer.

Lightbulb moment.

I've done my first nut replacement and I'm still dialing it in. That's maybe the most enlightening explaination I've heard yet. Thanks for the post in the other forum to direct us over here. I could have used the prompt a couple of days ago. ;)
 
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I've been making nuts for builds and repairs for a while. Typically, I make them out of brass stock.
I started with using a basic set of needle files to accomplish it, but eventually moved to actual nut file sets (Hosco) to do it.

Problem is, despite these files saying they are the gauges described and round-cutting, they tend to leave a wider slot than I want (strings rattle side to side) and they cut a squared off bottom.

The fix for me has been to use the gauge of the next smallest string to cut the majority of the nut solt (for example, .085 for the .105 slot), then use a needle file to fine-tune it to the proper size and shape.
I actually had one needle file that was super-slim tapered for the last 1"+ long portion that was perfect, but misplaced it and can't seem to find a proper replacement (others don't taper gradually enough, so I have trouble in the G string slot or with guitar nuts).

So with all that:
1) Is there a proper nut slotting file set that doesn't cut this poorly?
2) Is it because it's a metal nut material that these aren't cutting right? (ie, is the metal coming off clogging the teeth and dragging extra material with it?)
3) If one wants to find super-detailed needle files to fine tune these slots, is there a proper source for them that isn't just some random set of needle files that mostly don't come into play for nut slotting use?

Any help is much appreciated. If I can reduce the time it takes to make a nut, then I'm a happy camper.
 
I've been making nuts for builds and repairs for a while. Typically, I make them out of brass stock.
I started with using a basic set of needle files to accomplish it, but eventually moved to actual nut file sets (Hosco) to do it.

Problem is, despite these files saying they are the gauges described and round-cutting, they tend to leave a wider slot than I want (strings rattle side to side) and they cut a squared off bottom.

The fix for me has been to use the gauge of the next smallest string to cut the majority of the nut solt (for example, .085 for the .105 slot), then use a needle file to fine-tune it to the proper size and shape.
I actually had one needle file that was super-slim tapered for the last 1"+ long portion that was perfect, but misplaced it and can't seem to find a proper replacement (others don't taper gradually enough, so I have trouble in the G string slot or with guitar nuts).

So with all that:
1) Is there a proper nut slotting file set that doesn't cut this poorly?
2) Is it because it's a metal nut material that these aren't cutting right? (ie, is the metal coming off clogging the teeth and dragging extra material with it?)
3) If one wants to find super-detailed needle files to fine tune these slots, is there a proper source for them that isn't just some random set of needle files that mostly don't come into play for nut slotting use?

Any help is much appreciated. If I can reduce the time it takes to make a nut, then I'm a happy camper.
I con't help much. The files I use produce a rounded bottom to the slot, but I bought them so long ago that I don't remember where I got them. I do remember that they were not cheap.
 
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