Welcome back. Last month we finished up everything we needed to do at the ass end of the strings, this month we will complete everything we need to do at the neck and finish up the series on Vintage tremolo modifications.
The biggest problem with guitars coming off the assembly lines today is the amount of attention and time that their manufacturers spend on shaping, slotting and polishing the nut on their axes. How many times have you been in a music store, pick up a $1,000.00 plus axe and go to tune it and you hear that dreaded “Tang”. That’s the sound of a string that has been pinched inside a string slot that has been cut incorrectly. The string gets hung up in the slot until there is just enough tension from you turning the machine head to release the pinched string. “Drives me Nuts” (like the play on words here?). Now imagine a tremolo equipped Strat or similar axe that has the same problem. Every time you use the tremolo you are releasing or increasing the tension of the strings to vary the pitch and if the strings are getting hung up at the nut they will never return to the same pitch. This will always throw your axe out of tune. That’s why a locking tremolo like a Floyd is so effective. The strings are locked down at both the bridge and at the nut and do not pass over any friction points that can cause the strings to hang up or get pinched.
A well cut nut will let the strings move freely length wise, but at the same time hold them from moving too much from side to side. The first thing we need to do is check the depth of each string slot in the nut. Go back a few months and check out my column “Factory Specs Part 2” where I go over how to check out your nut action height. In this case, because we are talking about a Strat your string height, above the first fret, should be between .018 and .020 thousands of an inch. Check each string to make sure the nut slots have been cut to the right depth.
Here’s another more accurate way of checking the depth of your string slots. First, you will need to measure the height of your frets. If you have a new Axe with little fret wear, you can measure the height at your first fret. If you have an older guitar, measure the last fret on the neck where there’s less wear. Or, if you know what frets are installed on your guitar you need to get the fret crown height from the suppliers catalog. To measure your fret height, place a 6” straight edge across your frets. Now using your feeler gauge, measure the space from the top of your fret board to the underside of the straight edge.
Measure your fret height from the top of your fret board to the underside of the straight edge.
Now let’s say the height of your fret is .044 thousands of an inch, take your feeler gauge and add the .020 of an inch required for the clearance over the first fret. This will give you a total of .064. Set your feeler gauge to .064 and slide it under each string right next to the nut. If the gauge slides under without touching the string, then you will need to deepen the string slots. If the gauge touches the strings, then the slots are OK.
Note of Caution:It does not take much to cut a string slot too deep. One or two passes too much with a file and you can scrap a nut. So if you decide to deepen the slots yourself, take it slow and check your work often. If this is something you’re not comfortable with, take your axe to a good repair guy and have them file the slots.
If you’re feeling brave and decide to file the slots yourself, you’ll need a set of nut files and your trusty feeler gauge. You can get a set of nut files at most luthier supply stores like Stew Mac.
Before you start cutting the slots deeper, you need to determine the slot width, which in turn, will determine the gauge of the nut file you will be using. To do this, you need to know what gauge of strings you are using. Your string gauge will determine the width of the string slot in the nut. I typically cut slots on a nut about .003 to .004, thousands of an inch larger then the gauge of a given string. For example, if your bass E string is .046 then your string slot width should be between .049 to.050 thousands of an inch. If your treble E string is .009, then your slot should be between .012 to .013 thousands of an inch wide.
When you order a set of nut files keep in mind that you can work a .048 file by rolling it sideways to cut a slot .052 easily. Using the same technique a file of .010 can be used to cut a slot of .012. So you don’t need to order a whole bunch of different nut files. Three, double-sided files of .012 / .020, .026 /.032 and a .036/.042 gauge will do just about anything you need for a guitar. You can also order single-size files of different gauge for a little less cost if you prefer.
Examples of Double sided and single gauge nut files.
To file the string slot to the correct depth and width, take your feeler gauge and set it to the height required for your frets. For the sake of this exercise, we will use the .064 thousands of an inch that we talked about earlier. With the strings removed, lay the feeler gauge on your fret board up tight to the edge of your nut. You will use the feeler gauge as a back stop as you file the nut. In other words, file the depth of the slot until you come close to contact with the top of the feeler gauge.
Use your feeler gauge as a guide so you don’t file the slot too deep.
File the string slots level with the fret board for now. Don’t file all the way down to the top of the feeler gauge. Leave some material in the bottom of the slot to be removed later during finishing and polishing. Remember, take your time and double check the depth and width of the slot often. Once you are happy with the roughed out string slots, you will need to put a small back angle on the slot. By that, I mean angle the file in the same direction that the strings will follow as they pass over the nut and angle down to the tuner posts. Typically, a couple of passes with your nut file at around 5 degrees will be enough.
Just a couple of passes at 5 Degrees will put a back angle on the string slot.
Next, widen the slot slightly where the string exits the nut (i.e. where the string leaves the nut on its path to the tuners). What we are trying to do is reduce any points where we may incur friction between the nut and the string. Next, take your file and wrap it in some 1000 grit sand paper and polish the entire slot until you come into contact with the feeler gauge.
One other thing, the height of the slot above a string should only be about ¾ to ½ the height of the string, just enough material to hold the string in place under heavy playing, or when you are bending on a string.
String slots only need to be about ¾ to ½ the height of the string it is for.
The one last thing to do is lubricate the slot every time you change your strings. I like to use powdered graphite, it’s easy to apply to the string slots and the excess blows away easily.
Lots of Graphite powder for each string slot, Every time you change your strings.
Sounds like a ton of work, it is! That’s why they don’t do this type of thing in a factory. It would just add too much to the cost of an axe.
So far we have gone to a lot of trouble to reduce all the friction points that we have in a vintage tremolo system. By doing this we have improved the playability of the system and improved its tuning stability. The last thing we need to look at is the angle of the strings as they pass from the nut to the tuners. The optimal angle for your strings is between 5 and 12 Degrees.
String angles should be between 5 and 12 degrees.
Any more than 12 degrees and you are adding a stress point and friction to the nut. Any less than 5 degrees and your string will have the tendency to pop out of the nut slot. You can adjust the string angle by adjusting the height of the string tree(s) on the head stock and by winding your strings from the bottom up, instead of, from the top down.
The best way that I have found to correct string angles is to invest in a set of height adjustable post type tuners. Recently, I have been using “Gotoh” (HAP) tuners on my custom build guitars. They let you adjust the amount of angle on each string and are available in modern and vintage six in line design. I can’t say enough about the quality of these tuners and they won’t break the bank either.
So that’s it for the modifications to vintage tremolo units. I hope you have learned something and enjoyed it. Next month, we’ll get back to the set up series.
So Cheers, Be Good to Each Other and Remember
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