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here is an image of my fretboard and strings; is this the correct adjustment of the truss rod? Many Thanks!

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drugstoredir2014.com

You show the greatest amount of relief falling at the 12th fret. Usually, it should be closer to the middle of the fretboard, around the 6th or 7th fret. How much relief do you have?

It depends on a whole lot of things about the way the neck, heel and body are constructed but I think it is more like this



If you just consider the neck as a beam, string tension will pull a bit of an arc, but at the heel it becomes stiferf and as it becomes part of the body it becomes very stiff. From the heel on the geometry is pretty much set by how you anchor the fretboard to the top - does it drop off, stay flat, have a ski jump hump. The neck isn't uniform in cross sectional shape so it might bend a little more as it approaches the nut. Then of course you have that pesky truss rod (which might be one of several designs with its own bending characteristics).

We generally define "relief" as the bowing between the nut and the body joint - as you know it is normally defined by laying a straightedge from the first fret to the one at the body joint (a tight string is a convenient straight edge) and measuring at the greatest difference - that is usually around the 7th or 8th fret. Another nice way to measure the effects of relief is to fret a string at each fret and measure the clearance at the next one - an ideal board will have that number either stay the same or get gradually larger - in either of those cases you cannot have fret buzz.

I personally like to run as small a relief (measured in the conventional way) as possible, but that does require the frets to be perfect.

forgot to say this is on a PRS SE semi-hollow 2018 deluxe with a set neck.

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drugstoredir2014.com

I don't know how much relief I have, it arrived this way from a secondhand purchase. Looks like from what you and others have said that it needs pulling back a bit? cheers!

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drugstoredir2014.com

No! I absolutely did not say that. I said you need to measure your relief. Until you know the amount of relief you currently have, you should not touch the truss rod.

An approximation can be made by pressing a string down at the first and last fret and look at the largest gap between the bottom of the string and the top of the frets. Like I said, that should be near the middle of the fretboard. The largest gap should be around .007" which is about the thickness of a business card. If you have feeler gauges you can get a true measurement. And if you have an accurate straightedge you can get a precise number. Only then will you know if the truss rod needs adjustment.

Exactly one hundred percent what Barry just said. I have a standing rule that I never touch ANYTHING until I measured EVERYTHING. I also have a very good understanding of which setup parameters affect others - changing relief will affect action, changing action has has a negligible effect on relief. Measure it using the tensioned string - put a capo on at the first fret and hold it down at the body joint. My goal is 4 or 5 thousands, that requires that the frets are in good shape.

This might help

https://www.tdpri.com/threads/basic-setup.952636/

Hi,
...right, I have pressed down the 'E' string @ the 1st & 22nd frets; also 1st & 20th frets; ...then measured the gap between the top of the 12th & 10th frets respectively and underside of the string; the gap observed is approximately .25 - .30 of a 'mm'. in ALL these kinds of measurements! I have a steel ruler and observed that all the frets are flat & level. With the current bridge/saddle height the gap between the top of the 22nd. fret and the middle of the 'E' string is about 5mm (UNFRETTED). So, is this all OK please?

Also, @ the 12th. fret (unfretted) low 'E' string, gap is about 2.75mm.

cheers!

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drugstoredir2014.com

Freeman posted a link to his set up method. His advice is always worth listening to, and I generally follow the same sequence he uses.

When dealing with the relief I usually shoot for .1 - .2 mm of relief, this is subject to the condition of the frets, and the technique of the person playing.

For electrics I measure my action at the 17th fret, while holding the strings down at the first fret with a capo. I like the low E to be about 5/64" or almost 2mm, and on the high E 4/64" or roughly 1.6mm. Again how high or low you go depends on the technique of the player.

My personal preference is generally erring a little on the high side.

All useful information, thanks for taking the time and trouble to share your personal experience.

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drugstoredir2014.com

So, doesn't the height at the 22nd. fret matter, as long as it's correct at the 12th. & 1st (on 'E' strings)?

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drugstoredir2014.com

no

I don't like either of the two graphic images above to show relief because it shows that the fretboard plane goes down into a trough which it then has to climb back out of. The relief should be a gradual sloping profile starting at zero at the nut all the way to the body joint. No point X along the fretbaord should ever be higher than any of the points -X behind it. In those images for example the 14th fret is higher then the 7th which means the string has to 'climb' back out of a hole. I'm probably not explaining this well.

slope

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drugstoredir2014.com

I don't like my image either and I try my darnedest to keep it from happening, but unfortunately that is pretty common. With most necks the tension pulls relief in up to the heel where then neck suddenly gets very stiff and doesn't bend. Whatever happens there is a function of how the guitar was built what I try to do is make the fretboard extension follow the tangent of the end of the relief. By absolutely minimizing the amount of relief (which requires pretty darn perfect frets) and maybe paying attention to that transition area when the neck is built the affects can be minimized. I use that diagram more to show what is going on that anything absolute.

When I set up a guitar I have one last test that I always make. I fret each string at each fret and check the next fret clearance all the way up the neck. As long as that clearance stays the same or gets bigger I know the neck will play buzz free. It may not be optimal but at least it is pretty good. If the gap gets bigger in the center of the scale, then gets smaller as I approach the joint I've got the situation in the drawing - too much relief, a hump a the joint. I can work on that.

I think your drawing is a deliberate exaggeration, to show what is happening, to show what is going on? (as was mine).

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drugstoredir2014.com

Better, but I'd put that red line into more of a banana shape. But yes exaggeration is good to make a point too.

It is very exaggerated, but its pretty much what most necks look like. Think of the curved lower line as the tops of the frets, at the nut end the bottom of the nut slots can be thought of as a zero fret. It can approach the level of the other frets but never go below that.

Remember too how we measure relief - we put a straight edge (a taught string) between the top of the first fret and the highest fret at the other end of the board - that is almost always over the neck to body joint somewhere.

We also spend hours on this forum and on our work bench trying to deal with that pesky body joint hump. What to do with the fretboard extension - do we have a little fall off, is it flat, do we have the infamous ski jump? Do we play in that area (many acoustic players don't), if not can we more or less ignore it?

If you really want to get into modeling the shape and response of a guitar neck, start with a cantilevered beam, find the neutral axis, offset the string tension by the height of the nut and do an engineering analysis. It gets complicated real fast when you add truss rod and the changing shape and thickness as you move up the neck. There have bee some pretty good studies in lutherie literature,

For a good description of how relief interacts with the rest of setup, this is pretty good

http://www.bryankimsey.com/setup/neck_relief_1.htm

The images exaggerate the relief and fall-away (lower line), but they mistakenly do not exaggerate the rise of the strings above the frets (upper line) as you get closer to the bridge. If you did that then there would not be the hole to dig yourself out of, so to speak.

last go:

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drugstoredir2014.com