Saturday, April 25, 2015


While I've played my kit guitar a few times since I finished it a couple of weeks ago and I'm pleased with overall, it hasn't been entirely pleasant.  It was immediately (and somewhat painfully) obvious that the strings were much too high above the neck.  Those of you who are guitarists or know the basics can skip the next paragraph while I bring everyone else up to speed.
A guitar, ukelele, bass guitar, mandolin, banjo; basically any stringed instrument changes the pitch it plays by pressing the string down onto a board to make the vibrating portion shorter.  If the string is not pressed at all, it's supported in two places: the top is called the nut and the bottom is called the bridge.  All of the above instruments have wires called frets on the board that help you get the exact length reduction you want; violins, cellos, and some others don't have frets and just rely on accurate positioning of your finger.  Narrowing the subject down to guitars, the height of the strings above the fretboard (neck) is generally lower on an electric guitar than an acoustic, because the acoustic guitar player has to hit the strings harder to get louder sounds.  The electric guitar can use less string motion and make up for it with watts out of the amplifier.  The combination of the height of the strings and the ease of playing is referred to as the "action", and lowering the strings or speeding the action is one of the most common reasons players bring their guitar into the shop.

My guitar's problem was that the nut was too high.  Comparing it to the nut on an easy to play electric, strings were much higher.  More than 1/16", .062" or so too high.  The bridge is adjustable, nuts are not adjustable.  Some research showed me the generally accepted way of lowering the strings is to file the slots in the nut deeper. 

Nuts are complicated.
The problem with filing the slots is that is that each string is a different diameter, and the slot width should match the diameter of the string (a few thousandths slop is acceptable).  I typically use strings with diameters that run from .010 for the highest down to .046" for the lowest, and you don't just go find flat files .010 or .012 thick at the corner hardware store.  Nut files are expensive; a set of six (or three double edged files) is going to run around $80 to $100.  The exact amount of filing you do is going to have to be measured and while the technology isn't exactly rocket surgery, you really need something like this. You need to ensure that the fingerboard-facing edge of the nut slot is the highest point, because if it's too much farther forward toward the tuning pegs, that effects the ratio of the lengths when you press the string down.  The frets are placed based on the distance from the very top edge of the fingerboard to the bridge, and if the end of the string is too far forward of that edge, say 1/16" past the fingerboard edge of the nut, the ratios of lengths are not as intended.  Guitarists worry about intonation of the guitar; that every note is on pitch, (so that they can bend the note off pitch); this would affect intonation.  The 12th fret is exactly half the distance from the nut to the bridge (this is called the scale length, and there are guitars with different scale lengths), and intonation is adjusted by ensuring that the note at the 12th fret is exactly one octave above the open string.  This is adjustable at the bridge on most electric guitars.  

If you know me, you know I'm not too reluctant to buy tools, but if it's something I'm only going to use once, that does make me pause to look for alternatives.  Here we are at nearly $150 and we haven't even really started. 

It turns out I'm good friends with another engineer whose long-term partner retired from work seven years ago.  I knew this guy somewhat; we worked together on a couple of jobs, but with three engineering buildings and being reassigned between them as needed, it's easy to lose contact.  We had never spent time hanging out together outside of work.  Some time ago, I had heard he had been working as a luthier after retiring.  I asked her to ask him if he had a set of nut files, and if he'd mind loaning me the set for a weekend.  What I got was far better than that, an invitation to come over to his place and act like an apprentice to him on setting up my guitar.  That's how I spent the day. 

The first thing we did was measure the neck to see if the truss rod was set properly.  I did this with no instruments at all; he pulled out a neck relief gauge.  I had over adjusted it: you want it a little concave, and if I recall correctly I was about .018 low and he readjusted the truss rod to .010" low.  Next was to measure the neck radius, and verify the understring radius along the neck, down to the bridge.  One string notch in my bridge needed to be deepened a bit to allow the strings to follow the proper radius all the way to the bridge.  We checked frets for flatness, and found several that needed to be hammered down. 

Finally it was on to the nut, the only part I expected to work on.  The strings were all quite high, and more so on the thin string end, so my friend recommended we pop the nut off the neck, remove most of the thickness from the bottom, and then use the files to adjust out the last 25 mils or so.  Why?  This is a cheap kit, not a high-end guitar and he realized that it was a plastic nut - hollow on the inside - and was concerned we might cut through the floor of the nut.  High end guitars are more likely to have a nut made of bone or other solid material.  I won't bore you with a play by play here, but we did that by working the nut over several sheets of sandpaper until we took off about .040 across the bottom.  Then on to the files to set the final string height.  Once that was set, the nut was pulled and the top of it filed down until the strings sit with a good part of their diameters above the nut, as seen in the graphic above.  Finally, I re-stringed the guitar with a fresh set of strings

The difference is night and day.  My kit guitar now plays as smoothly and comfortably as any electric I've touched in the last several years.  It does give me some pause in recommending these kits, though.  It's not a bad guitar but when I consider the price, the complete lack of instructions and needing to do this extensive work, it doesn't seem like quite as big a bargain.  Musician's Friend has the Epiphone version of this guitar for about twice what the kit cost when I include the money spent on finishing this one.  You can cut that down even more if you go for a different brand.  Is it worth it to build the kit?  If you're on a strict budget?  Maybe.  The more you're set up to do it yourself, the more of the tools you can borrow or get access to, the better it works out.  My real goal here was to learn some of the skills needed; to build the guitar just to build the guitar. 

Now, if you don't mind, I'm going to go play it for a while!


  1. Great job!

    Always good to have friends with the equipment you need, and even better if they're willing to teach you how to use it!

  2. At least you didn't spend too much fretting over the problem....

  3. AuricTech - I was this close to saying "Guitarists fret over intonation...", but avoided the pun (for once).

    Someone had to go for the pun.


  4. I wonder if a guy could clamp a old section of guitar string in a jewelers saw frame, stretch it tight, and use a little carborundum paste on the string to act as a file? Seems like it might work, especially on the wound strings where the grit could have a place to set into.
    I have a very sharp edge jewelers file, and a tapered jewelers rattail I have used with some success for nuts.

  5. There's a dealer on eBay selling a jeweler's saw (like a coping saw) with a set of blades for most strings. The blades sound like files: "serrated stainless steel". It's very reasonably priced compared to a set of nut files. I think I've seen diamond blades like what you're referring to, also.

    I have no idea if it works, but I almost tried one. My guess is the old school guys who learned the old way will be slow to adopt it, while beginners may give it a try.

    (No connection to this seller, just saw it while I was looking, yada, yada, yada).

  6. I've bought some tools from these guys :

    And I just received an email from them advertising nut files.

    They also sell abrasive cord for the smoothing after you've used the files: