Slight bow in neck or not


#1

I was wondering what people prefer a slight bow or a straight neck . I can see the advantage of a slight inward bow as it would help the strings clear the upper frets thus making a cleaner note . I know that some players like to use the middle of the fret board so they actually bow the neck up a bit and making noting much easier. Some even tune down a full step “D” it makes it much easier to bend the strings , so any thoughts on this . Lonnie Mack comes to mind.


#2

I’m not a guitar repair expert, but I always thought a proper set-up should have a slight relief (bow) on the neck.

If you capo the first fret and hold down the low E at the twelth fret you should have a slight gap between all of the other frets and bottom of the string. It will be very minimul (almost no gap) at the second and eleventh frets and gradually have more gap as you move to the middle with the largest gap being between the seventh and eighth frets. I just checked my three “best” guitars since you stirred my curiosity, and they all have a relief with the biggest gaps being between 1/32" to less than 1/16". The Collings had the most relief, while the Taylor had the least. The Gibson was real close to the Taylor.

I don’t know, but I would think no relief could cause structural problems and buzzing. but like I said, I’m no guitar technician. Someone else may be better qualified to answer that question Welder.


#3

I like as little relief (as close to flat) as I can get without buzzing issues up and down the neck. On some guitars, that has been almost flat. On most my guitars it runs a hair more.

I think the function of the truss rod is something that is often mis-used. Many people think of it as a tool for raising or lowering the action. It does that as a side effect. The main purpose of relief is to allow the neck to start buzzing equally up and down the neck as action is lowered. Ferinstance… if I had a slight back-bow in the relief, while it might play fine around the 7th fret, the lower frets would be buzzy (if not unusable) and the upper frets would have higher action than needed. By removing the back bow, I could eliminate the low fret buzzing and I could lower the overall action at the saddle and/or nut. On the other hand if I have too much relief, the low frets would be buzz free, but the middle frets would get buzzy quickly as I lowered the action. Removing relief would remove buzziness from the middle frets and would allow me to lower the action further at the saddle.


#4

Hmmmm, you got me thinking Mike,

My Collings action is a little higher than my others, not bad, but could be a little lower. It also has the most relief and it has a through saddle, so I can’t cut down the bottom of it, or the extensions will be too short for the groove in the bridge. I know this because I already cut it down slightly (it is removable and not glued in, but it’s tight). Maybe I’ll try taking out some of the relief and see what happens. I can never remember which way to turn it though. For less relief, I believe I would want to loosen the truss rod to make it straighter. Right or wrong?

Like you said, it’s not a tool for lowering the action, but without ordering a new, shorter saddle from Collings, this may be worth trying. It’s also a compensated saddle, so it would be tricky to cut down the top of it.


#5

— Begin quote from “jwpropane”

Hmmmm, you got me thinking Mike,
For less relief, I believe I would want to loosen the truss rod to make it straighter. Right or wrong?

— End quote

Tighten the rod to reduce relief (make it straighter). I suspect you might well end up liking the results. The good news is… if you don’t, take it back to the way it was.

You mentioned shaping a compensated saddle: on my stage guitar it came with a Tusq saddle. For some reason, it wears pretty quick. About every three months or so, I have to smooth out the grooves on the saddle to prevent string breakage. I haven’t been trying to lower the action, but as a result of bringing the rest down to the wear height, it has lost some action height to the point where I will have to replace it soon. Anyway, long and short… you can take the height down from the top and then add the compensation back in as needed. I’d say I have probably lost about 1/32" off the saddle (resulting in the action coming down 1/64") and it still has some compensation left in it (without me trying to maintain the original compensation). I check it periodically, and I think my E and B strings are starting to get sharp enough for me to notice. I could add more compensation, but like I said, the saddle is about done. I have a bone saddle already fitted for it, I just need to get off my lazy posterior and bring it down to height.


#6

The relief of the acoustic guitar neck should be at about .010" to .012" between the bottom of the string and the top of the 7th/8th fret when depressing the 1st and last frets simultaneously. That is about the thickness of your first string (for reference). Keep in mind that different types of guitars will require different relief. A well made electric guitar can have nearly no relief, while an acoustic bass guitar has a larger relief. mandolins are nearly dead straight. No acoustic stringed instrument should have the strings lying on the fret when checking for relief (first and last fret depressed simultaneously).

The reason for the relief is to allow for the string amplitude (the width of the widest vibration of the string) when it is plucked.

As can be easily seen, the string vibrates widest at the center of the length of the string. Having a slight relief compensates for some of this amplitude and allows for a clean sound when plucked. Problems can arise when the action is too low and/or the relief is not enough to allow for string vibration width (buzzing, fretting out, poor tone, loss of volume…etc). However, as Mike pointed out, you definitely do not want to use the truss rod adjuster as a way to fix action that is too low or too high. This brings me to the part of this discussion where “how to set up your acoustic guitar” comes into play.

  1. Adjust the truss rod to get the proper relief (distances noted above).
  2. Cut the saddle height to the proper height for the player and his/her style of playing. Hard strummers need a higher action, light finger pickers can have a lower action. Action is measured at the 12th fret (underside of string to the top of the 12th fret).
  3. Cut the nut slots to get the lowest clean open tone.
  4. Adjust the intonation of the saddle. I will often cut the saddle to just slightly higher than the final height and then compensate the saddle so that the string plays in tune at the 12th fret (both fingered and played harmonic). A rule of thumb here is to check the intonation before you begin the set up so you have an idea how much each string will need to be compensated. Check the intonation again after properly setting the truss rod (more information). Getting the intonation perfect on an acoustic can be very difficult. However, getting it to withing a few cents of perfect is very doable and certainly will sound dead on to most folks ears.

At this point,if you have some dead spots or buzzing in a few areas of the fretboard, you need to remove the strings, loosen the truss rod to achieve a flat fingerboard and do a complete fret level and dress. Then reinstall the strings and tighten the truss rod to the proper relief measurements on the neck. Then enjoy.

If you find that you are having buzzing or poor tone over much of the fingerboard, you will need to raise the saddle to the proper height. You can do this by using thin strips of business card under the saddle to find the proper height. Once you have found the proper height, it is time to cut a whole new bone saddle using the height of the old saddle and business cards as a template.

If you have cut your nut slots too low, you will get buzzing or dead open strings. This sucks. At this point you can either try to repair the low slot by using bone powder/dust (from making your saddle) and some crazy glue filling the bottom of the nut slot. Allow it to completely dry/cure and carefully re-cut to the proper depth. Or, just make a new nut. :blush:

So, setting the truss rod to the proper relief is only one of many steps in getting your guitar to play properly.

One final thing, Truss rod nuts can stick or become bound up and hard to turn. NEVER FORCE IT! You can strip the nut or even break a truss rod by forcing an adjustment. A better way to deal with an overly tight truss rod nut is to unscrew it to the point that it comes off, put petroleum jelly in the threads of the nut and on the surface area that comes in contact with (faces) the rod, then reinstall it. You will find that the nut will be easier to adjust and less likely to strip or break.

Now get back to playing your guitar! :laughing:


#7

— Begin quote from “drguitar”

If you have cut your nut slots too low, you will get buzzing or dead open strings. This sucks. At this point you can either try to repair the low slot by using bone powder/dust (from making your saddle) and some crazy glue filling the bottom of the nut slot. Allow it to completely dry/cure and carefully re-cut to the proper depth. Or, just make a new nut. :blush:

— End quote

One other option is to shim the nut. I had a nut that was as close to perfect as they come and when I had some frets replaced, it was now too low. Bryan Kimsey shimmed the nut. He hardened the paper shim with CA glue (not while on the guitar). Frankly I can’t see it and I don’t think it affects the tone. It’s a pretty cool option and it really beat cutting a new nut. Making a new nut is demanding to get right.


#8

— Begin quote from “mreisz”

One other option is to shim the nut. I had a nut that was as close to perfect as they come and when I had some frets replaced, it was now too low. Bryan Kimsey shimmed the nut.

— End quote

Yep, I have done this also. And it is a viable option. Of course, this raises all the nut slots, not just the low one, so the other slots need to be cut to the proper depth. Which is still faster than having to cut a custom nut from a blank piece of bone. :wink:


#9

— Begin quote from “drguitar”

The relief of the acoustic guitar neck should be at about .010" to .012" between the bottom of the string and the top of the 7th/8th fret when depressing the 1st and last frets simultaneously.

— End quote

Thanks for your reply Doc.

When you say last fret, do you literally mean the last fret or the 12th fret. I checked my Collings with feeler gauges and at the 7th and 8th frets I have .016" while depressing the 12th fret with a capo on the first fret and I have .021" while depressing the last fret. (also checking at the 7th and 8th frets). Either way it appears to have too much relief.

I measured the action at the 12th fret on the low E using feeler gauges and it is about .099". I measured just so the gauges slide in without pushing up on the string. Using a ruler, it looks to be between 3/32" and 4/32" not at all bad for bluegrass. I’m thinking if I take out some of the relief, that may put it right at 3/32" and give me a proper relief as you mentioned earlier.

Also I should mention that I’m using medium gauge strings (.013 - .056).

Thanks again Mike and Doc.


#10

— Begin quote from “jwpropane”

When you say last fret, do you literally mean the last fret or the 12th fret.

— End quote

I press down both the first and last fret. Depending on the guitar, this could be the 18th fret, 22nd fret, 24th fret. On an acoustic guitar, the truss rod is actually only working on the frets from 1 to 14 (or 1 to 12 when the acoustic neck attaches to the body at the 12th fret). If you look carefully at your 14th to the last fret, you will see that the fingerboard is essentially flat in that section. So I measure from the first to the last fret which allows for any slight rise from fret 14 to last.

— Begin quote from “jwpropane”

I checked my Collings with feeler gauges and at the 7th and 8th frets I have .016" while depressing the 12th fret with a capo on the first fret and I have .021" while depressing the last fret. (also checking at the 7th and 8th frets). Either way it appears to have too much relief.

— End quote

Yep, that seems like your relief is a bit too much. If you have a particularly heavy hand or you need some frets leveled and dressed in the lower frets, the greater relief that you have will accommodate a cleaner sound to a certain point. Bryan Kimsey was mentioned earlier and he is a good reference for information in this area. He did a study of the fret clearances on a guitar with the same 12th fret action of .096" (only the relief was changed). The results are here.
http://www.bryankimsey.com/setup/neck_relief_1.htm

He mentions that he prefers a neck relief that is quite low. I believe he prefers his relief at .008 with the 1st and 14th fret depressed (nearly exactly the .010 - .012 I use when pressing down the 1st and last fret).

— Begin quote from “jwpropane”

I measured the action at the 12th fret on the low E using feeler gauges and it is about .099". I measured just so the gauges slide in without pushing up on the string.

— End quote

I like Bryan’s layout of string heights off the frets (action). I have used a similar system for the last 30 years and I love the fact that he has laid it out so clearly. A quick perusal should give you an idea as to how your action should be set.
http://www.bryankimsey.com/setup/actions.htm

It may be that your relief is too great, but when you set it properly, your action height will be a bit too low (requiring a new saddle or at least saddle shims). However, I believe when you get your guitar set up properly, you will be amazed at how nice it feels.

One last thing. Although I have been building guitars since I was 13, I am still learning with every repair and adjustment I do. As Firesign Theater put it, “I’m just another Bozo on the bus”… truly. It took me three adjustments, over the course of a couple of years, to get my Martin M38 just right, each time getting it closer to perfect. Electric guitars are easy to get right as you can just keep adjusting them with the strings on till it feels perfect. Acoustic guitars require you to remove the strings for action adjustment. So getting that right can often take quite a few sittings with the instrument. And it is very easy to take just a hair too much off the saddle which suddenly is causing all manner of tone loss and buzzing.

Slow and steady is definitely the rule here.


#11

— Begin quote from “jwpropane”

I checked my Collings with feeler gauges and at the 7th and 8th frets I have .016" while depressing the 12th fret with a capo on the first fret and I have .021" while depressing the last fret. (also checking at the 7th and 8th frets).

— End quote

On an acoustic guitar, normally from the neck joint to the last fret the action will rise a bit as frets “fallaway” from the strings, but that fallaway is primarily a function of neck angle as opposed to relief. But more to the point, that fallaway isn’t going to be directly changed with relief adjustments. As doc said, what you are changing on every acoustic I have setup is from the 1st fret to about the 12th fret. As a result, on an acoustic I measure by pressing at the 12th fret. There may be very minor neck shape changes with relief adjustments above that fret, but they are too small for me to notice. On an electric, the relief adjustment affects the almost the entire neck, so I generally fret at the last fret.

FWIW, there’s much discussion of measuring relief and such. To be honest, I find it nearly impossible to really accurately measure the clearance of a flexible object (string) against a rounded object (fret). It’s not like measuring a gap between two solid, fixed plates where a feeler either fits or it doesn’t. That’s ok as the big thing is not the absolute numbers but whether one can repeat the measurements with some reliability to compare different guitars. I don’t even use feelers for relief anymore unless someone wants a measurement. I just eyeball it to get close and then tweak based on what the guitar is doing when I play it. The absolute number is not important to me. What is important is that I get the neck as flat as I can without having notes fret out once my action height is set. That gets my feel and action height to my liking. Conveniently, I have found on most guitars if I set the relief to dead flat with no string tension, it will usually work out pretty close to what I like once the string tension is applied. With all that said, if I measured .016, that would be about double what I usually find optimal (but our measurements may not be the same).


#12

— Begin quote from “mreisz”

With all that said, if I measured .016, that would be about double what I usually find optimal (but our measurements may not be the same).

— End quote

Mike is right, .016 is a bit much for relief. After all these years, I also eyeball relief (I look for the gap to be about the thickness of the first string or smaller). And, the only way to really be sure you have it right is in the playing of the guitar (listening for noise and dead areas all over the fingerboard).

As Mike pointed out, every fingerboard is different (especially on acoustic guitars). Some will fall away from the strings beginning at the fret that meets the guitar body and some will lie nearly parallel to the strings starting at the guitar body. The worst of them will actually have a slight rise starting at the guitar body (a possible neck reset is in it’s future)! For the ones that fall away, you are essentially measuring the relief from the 1st to the 12th or 14th fret.

Also, as Mike said, depending on the guitar player, you can set the relief nearly flat as long as their (hard) playing does not cause undue tone loss and fret noise.


#13

If you set the neck perfectly flat,it gets hard to play as there is not enough relief, so I usually set at .003 for starters, but a Plek machine solves it all! J :mrgreen: erry


#14

I just got a guitar out of the shop… Had a bone bridge carved for it. The tech had a great trick.
The ball end of strings… Especially the thicker ones are thicker where the wire wraps back on itself.
She mentioned slipping the round ‘grommet’ (from a used string) onto the Bass string before pushing in the bridge pin. That sets the string in farther and allows the string to lay more solidly on the bridge.


#15

I will try that next string change , It might be a nice thing to do . I wonder if I could tell a difference at my age LOL .


#16

Martin’s spec for relief is 0.004 to 0.010". The string height is five to seven sixty fourths for e and for e’ four to five sixty fourths. All this depends on playing style, string tension and personal preference. I like four and three with 0.04 relief and light gauge strings; that would clearly not work for someone else. My classicals have the relief planed into the ebony fb and my lutes have virtual relief by scaling the diameter of the frets (made of gut and tied on the neck). The most interesting method of setting or adjusting relief is by varying the fret slot and fret tang thickness as done by Martin for the necks without adjustable truss rods. There is a guy who has posted a video on utube on compression fretting – looks like something for experts.


#17

We sure got the mother lode of information out of this post, thanks to all who posted here .


#18

You mentioned petroleum jelly to keep the truss rod easy to turn the nut. I use Never seize it is an old standard I used when I was a machine repairman for this one company I worked for . it will not allow the nut to stick and it will protect it from salt water , that comes in handy when you play your guitar while in the ocean LOL. it does not take much at all just a real light coat ( funny) hee hee ,… it is a good product .