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Fitting and cutting a replacement nut

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Fitting and cutting a replacement nut

PostPosted: Sat Aug 29, 2009 3:38 am
by zenguitar
I promised to post something about cutting and fitting a replacement nut so here is the 1st instalment.

James handed over his guitar a couple of days ago and I got the new strings and a bone nut blank yesterday. So I spent a few hours today getting started. The old nut is removed and I've already thicknessed the bone blank and I'll post some pics with the details later. I also planed the bridge because it was way too high to take a proper set-up and levelled, profiled and polished the frets.

But to start off I'm posting a pic showing the tools I'll be using.


My recently acquired StewMac nut tools are on the left. But you don't need those to do the job so I've also included my old files and saws on the right. They have done a perfectly good job on hundreds of nuts over the years. As I use the different tools I'll explain more about them and include pics. The only unusual items there are the half pencil and the piece of string on the Brasso tin and they are both very useful.

Next post coming as soon as I've edited and uploaded the pics.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Sat Aug 29, 2009 10:41 am
by Stonehousestudio
Sticky these please!


Re: Fitting and cutting a replacement nut

PostPosted: Sun Aug 30, 2009 2:44 am
by zenguitar
Consider it done.

I've just edited some more pics to upload which I'll do tomorrow together with the next steps.

Andy :beamup:

next steps

PostPosted: Mon Aug 31, 2009 12:26 am
by zenguitar
The first thing to do is remove the old nut.


Use a sharp blade to neatly and carefully cut along the edges of the old nut so that you don't damage the finish when you pop it out. Then place a block of wood against the old nut and give it a few gentle taps with a hammer to pop it out. And don't throw away the old nut, you will need it later.



Then it's time to clean up the the nut ledge/slot. I use a very sharp chisel. Carefully removing the remnants of glue from the end of the fretboard and ensuring that the bottom of the slot is good and flat too.


Until you end up with something clean and level waiting for the new nut.


You then need to thickness the nut blank. For a Fender style slotted nut you need to ensure its a snug fit in the slot, fitting well but without needing any force to get it in. For a Gibson style nut you can use the old nut as a thickness guide.

When I have a full workshop up and running I use a bench mounted disk and belt combination sander for rough thicknessing and shaping as it can save a lot of time. But for this example I'm using wet & dry paper and working by hand.


You need to take care to ensure that you keep the new bone blank evenly thicknessed and perfectly flat. You will see from the pic that I have a piece of plate glass set into my work bench. It's not essential, but I have found that it's useful to have in the workshop whenever you need a good, true, flat surface.

Once you have the blank to thickness you then need to flatten the bottom and ensure that it is square to the side. And don't forget to mark the blank clearly on the good face so you don't forget which is which.


In the next instalment I'll be trimming the thicknessed blank to size, marking out and starting the nut slots, shaping the back of the nut, polishing it nicely, then fitting the nut and finishing the slots to the right depth.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Mon Aug 31, 2009 8:04 am
by wave1
Thanks for this Zen - good stuff!

Re: Fitting and cutting a replacement nut

PostPosted: Tue Sep 01, 2009 1:51 am
by zenguitar
As promised, here we go again.

With the nut slot/shelf tidied up and the blank thicknessed I trim the blank to the width of the neck. I mark it simply with a pencil..


.. and then I use a saw to trim it down slightly oversize. I use a jewellers piercing saw with fine blades purely because I have one anyway for inlay work, but any fine cut saw will do. Then I use files and wet & dry paper to bring it down to the final width and match the profile of the fretboard edges so it's nice and smooth to the touch with no rough edges.

With the nut blank at the correct width it's time for the half pencil. I hold the blank firmly in place and use the half pencil to mark it with a datum line that is level with the tops of the frets...


... like so, leaving a mark like this.


Although it is perfectly possible to do the job without the reference line, it can save a lot of time having the reference mark. It enables you to mark out the location of the fret slots and cut them close to the final depth without having to do a series of trial fittings on the guitar itself.

Once I have the fret top datum line I mark another line about 0.5mm above it as a guide to the final slot depth. And about 1mm above that I mark another line which is the guide for the top of the nut.


Now I can put the blank into a vice and file it down to the line ready for marking the fret slots. I don't file the top flat, instead I ramp it so that the top is sloped. The highest point is the front of the nut and it slopes away towards the tuners. Like this...


With the blank at the correct width and thickness and close to the final height it's time to mark and rough cut the fret slots. Remember I said to keep the old nut? This is because it comes in very useful for marking the slot positions on the new nut. I transferred over the locations of the outer strings by eye and then used my StewMac string spacing rule to mark out the 4 inner strings. You can transfer over all 6 strings from the old nut or manually divide the space equally if you prefer.

The string spacing rule makes a very subtle difference. If you space the slots equally it can sometimes feel as if the bass side strings are closer together than the treble side strings because the strings are of increasing thickness. The StewMac tool very slightly increases the gap between strings as you move from treble to bass so that the gap between the strings are equal instead of the gaps between the string centres being equal.


With the slot positions marked it's time to start cutting. I prefer to use a triangular file to notch the locations before cutting. If you are slightly out of position on the first attempt the triangular file makes it easy to 'ease' it back into line. Then it's time to grab the saws and files and start cutting. I put the nut into the vice and use the saws and files to cut the slots to the guide line I made earlier and then drop the nut into place on the guitar to cut the slots close to their final depth.


I try to get the angle of the slot halfway between parallel to the strings and parallel to the break angle and headstock. Once I've finished the photo description I'll draw some diagrams and give a more detailed explanation of why.

But with the slots cut close to depth I can now trim the top of the nut down to it's final height. I do this with the files and wet & dry paper. The aim is to reduce the height of the nut until the wound strings are sitting halfway in and halfway out of the nut and the plain strings are just inside the nut. If the strings are too deep in the nut you get friction problems. And after further trimming, the nut looks like this.


Now it's time to finally shape and polish the blank ready for final fitting.

I use files and wet & dry paper to round the back of the nut as well as the sides. I just sand away until I have a nice shape and feel. Like this...


A lot of people will stop at this point and move on to the final fitting. But I like to go a stage further and polish the nut with 000000 wire wool like this...


Which looks and feels a lot better. But that's still not good enough for me. So I dig out the Brasso and a cloth and give it a further polish so that it's perfectly smooth and very shiny. Like this...


Partly it's because I like to do a job right and bone looks and feels great when you give it this much attention. But I also feel that if you can't be bothered to properly finish the parts a customer can see, how can they trust you to finish the parts they can't see? And tomorrows post will make that much clearer.

Final stage for today is to finally attach the nut to the guitar. All that's required are a couple of tiny drops of superglue. String tension is more than enough to hold a nut in place. The superglue is just there to stop it dropping off or slipping out of place.


I put the nut in place by hand and press it down until the superglue grips. Then I drop the strings in place so they can clamp it overnight. Don't forget that superglues need to be left overnight to develop their full strength even though they set in seconds.


Tomorrow I'll finish off by bringing the nut slots down to their final depth and reveal the Holy Grail, the difference between a good nut and a great nut.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Wed Sep 02, 2009 1:20 am
by zenguitar
Final instalment.

With the nut polished and glued in place it's time to tweak the nut slots down to their final depth. The final depth depends on the guitar and the players requirements and is measured as the clearance between the bottom of the string and the top of the 1st fret. I was taught to start with a 0.5mm gap for the bass E string and a 0.4mm gap for the treble E string and then work down from there. When starting out it's best to use a set of feeler gauges to measure the gap. Once you are at that point you can go lower but it's a matter of playing it by ear. Pop the string you are working on out of the nut slot and make a couple of gentle strokes with the saw or file. Then pop the string back into the slot and test. When the string buzzes against the top of the 1st fret, you've gone too far. At that point you can either start again with a new bone blank, or you can learn the art of filling the slot and re-cutting it ;)

Having cut hundreds of nuts I no longer use feeler gauges, I do it all by eye now. And one handy hint is to polish the 1st fret so it clearly reflects the string. I watch the gap between the bottom of the string and it's reflection as I work lower. That gives a very good visual guide. I also pluck the open string and watch it's reflection in the 1st fret as that gives the best visual indication that you are approaching the point where it might start buzzing. I also fret the string behind the first fret to see how it feels. It should be no harder to press down than the same string barred at, say, the 5th fret and then fretted at the 6th fret.

Getting the nut slot depth right is really important. Most mass produced guitars leave the factory with the 1st fret action too high. The reason is simple economics, the skilled labour and time it takes to do it right cost too much and when it's done by semi-skilled labour the cost of removing and replacing the nuts where they cut too deep is even higher. The factories operate with such small margins that the cost of replacing a badly cut nut could be more than they make in profit on a guitar.

Now, once the slots are at their final depth it's time to finish the job properly. And that's what I meant by The Holy Grail. Far too often people don't pay enough attention to the cutting and finishing of the slots. I've drawn a few examples on a whiteboard and photographed it, as it was a lot quicker than trying to do the same on PC...


A/ shows a slot cut flat. The problem here is that when the strings vibrates up it lifts away from the bottom of the slot and buzzes in the slot.

B/ shows the slot cut to match the break angle to the machine head. While it solves the problem in A/, it introduces problems of it's own that are less obvious but just as difficult. The first problem is that you can't guarantee the break angle to the machine head, if the string doesn't wind down the post low enough it no longer touches the slot at the back and can buzz in the slot again. It also puts a lot of pressure on the front edge and over time it can wear it down. That will lower the action further until it starts buzzing on the 1st fret.

C/ is pretty much ideal, it ensures that the string is pulled into the slot at the front and rear avoiding buzzing and also minimising the risk of wear on the front edge lowering the action.

In D/ I've tried to show how the bottom of the nut slot is still rough after you finish with the saw or file when you examine it closely.

That roughness is a cause of friction and can lead to the string sticking in the nut even though the slots are at the correct width. Regrettably, a lot of techs will cut the slots with saws and files and leave them exactly as the tool finished them. However, a decent luthier will go a stage further and finish the slots properly. The most common way is to use a piece of very fine wet & dry paper folded in half. The fold is inserted into the slot so that some of the grit polishes the bottom of the slot. But that is far from ideal, and the paper is too thick when folded to use in the plain string slots.

About 10 years ago I was studying jewellery and silversmithing and came across the Jewellers Mop made from a piece of string.


It's simply a piece of string doubled over, tied in a stopper knot just below the bend and with the individual threads teased out below the knot. Jewellers use this with abrasive paste, like rouge, to smooth and polish fine fretwork (small holes cut into metal).

I put 2 and 2 together and started using a mop with Brasso to polish fret slots so that they are nice and smooth.


Just like that. And you can see from the earlier pics how well Brasso polishes bone.

This is something I've kept to myself for a long time, but it is why I have so often been insistent that a well cut bone nut is as good as anything else available. And in the last few years StewMac have started to sell abrasive cord for exactly the same purpose. However, the cord is nowhere near as versatile as the jewellers mop. You can load a mop with whatever abrasive you need and it will go far finer than the cord too.

So, there you have it. How to make and replace a bone nut in next to no time. It's as good as any alternative material in performance and sounds better. And my personal record for making and replacing a bone nut for a strat is 15 minutes (that was with the use of my disk and belt bench sander). And yes Jef, I was thinking of trying to beat that record at the next Analog to Digital ;)

Any questions, please feel free to ask.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Wed Sep 02, 2009 6:28 pm
by Stonehousestudio
Thanks Andy!

That was brilliant, I really appreciate the effort mate and all the tips.

I think you're on a winner here mate.

Next stop "The Little Zen Book of Guitar Maintenance" available at all good book stores...


Re: Fitting and cutting a replacement nut

PostPosted: Wed Sep 02, 2009 7:30 pm
by subsonicworld
Yeah. This is top stuff.

You didn't once write something about maintaining motorcycles did you?... ;)

Re: Fitting and cutting a replacement nut

PostPosted: Wed Sep 02, 2009 8:36 pm
by Dan LB
Thanks a million Andy. That's very useful! I never knew about the Brasso trick. I've always left nut slots the way the file finishes them. Top job!


Re: Fitting and cutting a replacement nut

PostPosted: Thu Sep 03, 2009 12:47 am
by zenguitar
subsonicworld wrote:Yeah. This is top stuff.

You didn't once write something about maintaining motorcycles did you?... ;)

Nah, that was some other bloke. If I'd written Zen and the Art of Motorcycle Maintenance it would have actually been about Motorcycle Maintenance not about angst. But seeing as you mentioned it, here's a really handy Motorcycle Maintenance tip...

If you ride in the winter, get one of those hand pumped pressure sprays they sell in garden centres. Fill it with water and a few drops of washing up liquid and put it in the garage. When you get home from work just give it a few pumps and then spray the engine and underside of the bike before garaging for the night. And while the bike is drying, top up the sprayer. That will help prevent the ravages of winter salt.

Dan LB wrote:Thanks a million Andy. That's very useful! I never knew about the Brasso trick. I've always left nut slots the way the file finishes them. Top job!


Cheers Dan, I'm not surprised that you never knew the Brasso trick, I am not aware of anyone else doing it. I only worked it out myself because I spent a year at art college studying jewellery and silversmithing AFTER I trained as a guitar maker. You could also use the jewellers rouge paste that Dremel dealers sell in small packs. It's cut is more aggressive than Brasso which can be useful. The saw StewMac supply for 10 gauge slots has a very coarse cut, a far lower teeth per inch count than an X-Acto saw blade. So it might be worth making a second mop to use with the rouge, which I have done in the past.

Another tip for X-Acto saw blades is to stone the set off the teeth at one end of the blade. That way you can cut 9 gauge slots with one end and 12 gauge with the other, for example. I have a very nice backsaw that I keep for cutting fretslots, the kerf was a little too big initially but a light stoning made it perfect.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Thu Sep 03, 2009 11:30 am
by Jumpeyspyder
Fantastic Zen 8-)

Although am disapointed that you missed the step that involved the coffee in the first picture. ;)

I now very tempted to try making new bone nut on the cheesegrator.

Is there an alternative to a full set of proper nut files ?

Re: Fitting and cutting a replacement nut

PostPosted: Fri Sep 04, 2009 1:01 am
by zenguitar
Don't worry Jumpey...

I drank the coffee and a few more besides. Great coffee is another of my passions.


These are some basic files you can pick up for around £1 per set. Two are simple rat-tail files (one diamond the other traditional) that have a round section that tapers down. The other is a flat file that is ideal for cutting grooves.

All are very cheap to buy, a local model shop is the perfect place to find them. And all 3 will do a good job if you work carefully. One of the tricks you can learn is to rock the file from side to side to make a slot slightly wider.

All bone blanks are a lot wider than the neck. One handy hint it to use the piece or pieces you cut off to practice on with your nut files. And when we had a greenhouse in the past, I used to get old bones from the butcher. I would boil them up hard for an hour or so to get rid of the meat and fat and then cut them down into blanks and leave them to dry out in the green house. That gave me plenty of blanks to work on to get to know bone and my files/saws.

Andy :beamup:

Re: Fitting and cutting a replacement nut

PostPosted: Mon Sep 07, 2009 1:27 am
by Dan LB
Zen, I had the Brasso out today!. Our guitarist has been consistantly breaking strings in rehearsal. The strings kept breaking at the saddle so I reckoned I'd try your mop trick to smooth out the slots in the saddles. So far so good. Cheers!


Re: Fitting and cutting a replacement nut

PostPosted: Sun Oct 11, 2009 11:02 pm
by octavedoctor
Damn fine work Andy, almost exactly as I would have done it. however i gave up on the old half pencil a while ago; I now use a billet of the graphite composite I use for making graphite nuts.