Setup- Fret Crowning and or Nut adustment

[BiscoDrew]

Let's say I have two archtops. Both are strung with the same set of strings and both nave virtually identical neck relief (which is to say virtually none at all, say < .06 mm at the 7th fret while depressing the 1st fret and the 12th fret where the neck meets the body). One has a higher action, roughly 1/16th at the low E 12th fret, with a height of 31/32nds of an inch (24.61 mm) from the soundboard to the top of the saddle. The other has a lower action, slightly less then 1/16th of an inch at the low E12th fret, with a height of 26/32nds of an inch (20.64 mm) from the soundboard to the top of the saddle. This is the lowest the saddle can be lowered without any buzzing on each instrument.

Firstly, I know I need to invest in an action ruler. I do have feeler gauges but I find them unreliable for measuring action. The measurements of the action are approximations but the other measurements are accurate and double checked. The action at the high E is very close to that of the low E- the saddles are fairly uniformly straight across, not higher or lower on one side.

Secondly, I didn't attempt to measure the depths of the nut slots. I know this information would be helpful.

Does this sound like the frets need to be addressed or the nut or both potentially?

I'd like to set up the second guitar to get a lower action if possible. I know this is getting into hair-splitting territory, but I'm trying to inform myself and would appreciate any insight from someone who does a lot of setups.

[sgosnell]

Most archtops I know of have the neck meet the body at the 14th fret. But that's really irrelevant here. Fret buzzing, IME, on higher frets is caused by uneven frets. Nut slot heights does affect action, but when you fret a string the effect of the nut is removed. If the frets are indeed uneven, the higher frets should not produce the same buzz. There can be a rise in the fingerboard above the body join, which can produce buzz even if the frets are all of identical height. This can possibly be addressed by lowering and recrowning (leveling) the frets in some cases. It's also possible in some cases to straighten the entire neck by tightening the truss rod even more, which can sometimes pull it all straight. Judgement is needed if you try this, to prevent breaking the truss rod off. What you really need is a straightedge which has cutouts for the frets, to measure the straightness of the entire neck. StewMac sells these, as do some other luthier suppliers. But the bottom line for me is that it's not possible to say precisely what the problem is without actually checking the guitar. Anything I say is merely speculation, based on my own previous experience.

[Jimmy blue note]

Most archtops I know of have the neck meet the body at the 14th fret. But that's really irrelevant here. Fret buzzing, IME, on higher frets is caused by uneven frets. Nut slot heights does affect action, but when you fret a string the effect of the nut is removed. If the frets are indeed uneven, the higher frets should not produce the same buzz. There can be a rise in the fingerboard above the body join, which can produce buzz even if the frets are all of identical height. This can possibly be addressed by lowering and recrowning (leveling) the frets in some cases. It's also possible in some cases to straighten the entire neck by tightening the truss rod even more, which can sometimes pull it all straight. Judgement is needed if you try this, to prevent breaking the truss rod off. What you really need is a straightedge which has cutouts for the frets, to measure the straightness of the entire neck. StewMac sells these, as do some other luthier suppliers. But the bottom line for me is that it's not possible to say precisely what the problem is without actually checking the guitar. Anything I say is merely speculation, based on my own previous experience.

+1 on this nugget of information. snogsnell talks the talk like he walks the walk.
Can be a number of things. Further advice without hand-on is fraught with danger and disaster. Find a good luthier and stay in his/her good graces.
Humble 2 cents

[BiscoDrew]

I just find the guitar with higher action slightly less enjoyable to play. I know the action is pretty low as it is. I am confident that the truss rod is about as tight as I want it- I did give it a couple judicious tweaks in the tighter direction and this didn't alleviate the issue so I backed it off back to the way I had it set all along. I guess what I was trying to figure out was whether the frets could be sanded a bit lower to get that action down or whether the nut needed to be looked into.

I was under the impression that nut slot depth DID impact the action/playability of the instrument. So you're saying that it only impacts the action of open strings and intonation in the first position (string buzz on the first few frets, too) because once fretted the nut becomes a moot point? Makes sense to me.

I feel like if the variables are all very similar from guitar to guitar the only thing that it could be is the overall height of the upper frets (the area where I get the buzz once I lower the saddle beyond the sweet spot).

I'm trying to learn how to do these things rather then pay someone else to do it- I'm interested in repairs and lutherie for myself. Maybe I should try and find someone to dress the frets who would be willing to let me look on while they worked. Fret work is definitely on my list of skills to acquire. I have seen that tool you mentioned and I plan on picking one up from stewmac.

Thanks

[BiscoDrew]

I see what you mean about a potential hump and uneven frets. I'm sure I could get a better idea of whats going on with the overall straightness of the neck then what I am currently able to determine for myself with the tools I have on hand,

[BiscoDrew]

Most archtops I know of have the neck meet the body at the 14th fret.

I miss-typed. I meant the relief measurement was taken at 7 while depressing 1 and 14.

[sgosnell]

Nut slot height does affect action. I may not fully understand where the buzz is occurring. If it's all along the neck, then it might be time to look at the nut. Depth of the slot is completely irrelevant, because the height of the entire nut is variable. The important measurement is the height of the strings above the first fret when at pitch. I prefer the height to be the same as the height of the string above the second fret when the string is fretted at the first fret, which requires the height of the bottom of the slot to be the same distance above the fretboard as a fret. So I file the slot using depth gauges as a guide up against the nut, the same depth as the frets, plus a few thousandths of insurance. Go slow on the final few thousandths, it's easy to go too deep. UV resin is my chosen method of filling slots cut too deeply. Make very sure you have the proper relief in the neck before you start, because it's easy, and common, to have a nut with perfect slots, then remove relief and have the strings buzz on the first fret. The usual setup just avoids this by having the slots a little high. Factory guitars avoid it by having the nut slots waaayyy too high. Another way is to use a zero fret, such as the Zero-Glide system. Choose the right fret size from those in the package, install the replacement nut with the zero fret properly, and there is no need to fiddle with nut slots. It is tedious work to get everything to fit properly, though. The quicker way is really to get the existing nut slots done properly. You will need the proper files, which can be expensive. For a one-off, you can make your own nut files from depth gauges, using a sharp file or a Dremel or similar with a cutoff wheel, to put sawtooth edges on the gauges, then pick the proper gauges to get the slot width for each string. Or you can take the guitar to a tech and hope he knows what he's doing. Some do, some don't. It's a jungle out there. That's why I've been doing my own for 50 years or so. Your first efforts won't be perfect, so I advise doing only a little, playing it for awhile, and doing a little more at a time, several times, until you get it right. But if you overdo it, it's still recoverable, one way or another.

[Jimmy blue note]

I was under the impression that nut slot depth DID impact the action/playability of the instrument. So you're saying that it only impacts the action of open strings and intonation in the first position (string buzz on the first few frets, too) because once fretted the nut becomes a moot point? Makes sense to me.

It does make a huge difference. Optimizing action applies to the entire length of the fingerboard. A string is a straight line. How it's set at either end relates to the entire geometry of the string, but some people play harder, need more clearance to avoid buzzing, or heavier string gauge gives more tension so that means less flex and flop-and lower possible action. Some people like a little growl. Some people need more relief. Some people want action so low that you breathe, it buzzes... all these things take different action, different relief and all of this is undermined by a high string clearance at the nut.
Set the nut...then set the bridge. Order of operations.
I look at the string as the last ray of sunlight over a landscape, or a beam of laser light. If the sun is shining over a high point at the nut, you can see further and your bridge point can be lower bringing the higher frets to a potentially lower point. But in this configuration, if you want a lower action at lower frets, and the better note accuracy and ease that comes from that, lowering the nut is going to change everything to some degree and that beam of light is going to catch every mountain, hill and eventually higher point along its run. Lower the nut end height, after you've addressed the frets (made the landscape into a salt flats) and you can get a low point at the other end of the beam of light. Everything on the ground is close to the beam. Ridiculously low action for someone with a light touch.

I set my own action at the nut to a height equivalent to the height under the string at the second fret when the first fret is depressed; it's called zero fret height and it's perfect for me. I don't use feeler gauges, I use my eye and fingers-that's just me. Downside is one too many swipes of the fret file and you have a buzz. Ouch. Then you have to fix that...another story. There is a reasonable range of really comfortable close tolerance nut height.

I worked for Ibanez. They were ALL set up too high...for good reason: You never know if it's going to the next thrasher with an anvil forearm. But this is your guitar, you can optimize.
Yes get the tools, teach yourself. You'll feel great. You'll play better.

Here's my order of operations:
Remove the strings.
Adjust the fingerboard relief for dead on straight (measured from the wood) with the truss rod.
Tape the fingerboard to protect it.
Level, crown and polish the frets to absolute straight. Take any offending fret ends down at this point.
Remove the tape and clean up, oil and treat the fingerboard.
String up the guitar with the correct string gauge. To pitch. NEW strings!
Relieve the neck to the amount of bow you need.
Set the string height at the nut. Check the relief again.
Set the height at the bridge, easier on a thumbwheel guitar, and more difficult on a flat top.
Set the bridge/saddle/saddle pieces for intonation.
Let the guitar settle in and check this again.

That's the string and neck part of a good setup as I do it-in general. Different people use different tools to do this, but this is the idea.

Practice, patience and experience were my best allies. I apprenticed with a classical builder, then an archtop builder and I'm still picking up tricks.
So happy you want to learn the craft. It's in your hands now.

Dang sgosnell, you must've posted that fine post while I was writing this. Pardon any redundancy. Excellent information within that one.

[BiscoDrew]

Thank you so much for the helpful tips!

Its a shame there aren't more apprenticeship opportunities (or a blessing, after the deep knowledge is attained anyway). It would be my dream job to repair instruments and make my own. I'm working toward that slowly. Have done a couple repair and flips and really getting into it. Always appreciate the wisdom on these boards.

[vintagelove]

I just find the guitar with higher action slightly less enjoyable to play. I know the action is pretty low as it is. I am confident that the truss rod is about as tight as I want it- I did give it a couple judicious tweaks in the tighter direction and this didn't alleviate the issue so I backed it off back to the way I had it set all along. I guess what I was trying to figure out was whether the frets could be sanded a bit lower to get that action down or whether the nut needed to be looked into.

I was under the impression that nut slot depth DID impact the action/playability of the instrument. So you're saying that it only impacts the action of open strings and intonation in the first position (string buzz on the first few frets, too) because once fretted the nut becomes a moot point? Makes sense to me.

I feel like if the variables are all very similar from guitar to guitar the only thing that it could be is the overall height of the upper frets (the area where I get the buzz once I lower the saddle beyond the sweet spot).

I'm trying to learn how to do these things rather then pay someone else to do it- I'm interested in repairs and lutherie for myself. Maybe I should try and find someone to dress the frets who would be willing to let me look on while they worked. Fret work is definitely on my list of skills to acquire. I have seen that tool you mentioned and I plan on picking one up from stewmac.

Thanks

Nut slots definitely effect the action, especially apparent stiffness.

Try dropping your action on the high e string as low as it will go before completely fretting out. Now go fret by fret up the neck, at some point you may reach a fret where the buzz decreases or stops altogether, that will be the high fret. It doesn't work every time, but it's a solid technique that has caught what luthiers missed with their tools.

For just touching up a nut slot, the cheap welding rods that people pass off as nut files will probably work. They did for me just recently, worst case you're out five bucks. Hope that helps.

[sgosnell]

Not welding rods, they're for cleaning the tips of torches. They work, but very slowly, which can be a blessing or a curse. They're more useful for dealing with string slots on wooden saddles, which are comparatively softer than bone. A set of feeler gauges is about as cheap, and more useful once you get teeth on them.

[BiscoDrew]

Nut files have BEEN on the shopping list. Surprisingly expensive, some sets.

[Jimmy Smith]

^ Yes, the files are expensive. You just have to get them even though they are a ripoff. Get the gauges too.

Seems there's already accurate advice here. I'll address the point of buzzing at the upper frets. This can be caused by too much bow - if the relief is deeper in the middle of the neck than at the heel. However, if you have set the neck straight by adjusting the truss rod and it still buzzes, then by definition the frets at the heel are too high and you have to either spot level there or level the whole neck. I like to always do a level on a new neck because I like having everything perfectly level to accommodate any action. However a level isn't always required. It can be on a case by case basis. If there's no buzzing at the action that you want to play at, then good to go.

2nd that height at the nut has a big effect at how high the action is overall. If you want low action, you'll want to finesse getting low action at the nut as well. My go to numbers for nut height are .016" - .020" staggered e - E for low with no buzz and .018" - .022" for medium but won't press the note sharp.

You can teach yourself this stuff. I taught myself and now do quality fret levels with rounded ends, crowned so the peak is in the center, and brought to 2000 grit. Every note plays perfectly at any action. Don't learn on nice guitars tho, get cheap necks and practice on them.