If I may... would like to question the experts regarding truss

mistermikev

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so... first let me acknowledge that this topic has been covered a lot... using google to search and reading many threads on the subject but still wanting more. basically trying to study the greats. Interested specifically in trying a rod style truss.

I am aware there are those in the "the originals were sloped but straight" as well as "sloped doesn't work do a bow" camp - do not wish to start that debate.

In short, I would be very interested in seeing a document/diagram/cross-section of the truss-rod/neck for both designs do they exhist?

concerning bowed: is there a "known" curve that was used in the lp? ie known radius to the channel?
concerning slope: as I understand (correct if I am wrong) the slope rise/run would be .125" over truss rod length? per mr @pshupe 5/8" at the body and 1/2" at the headstock?

additional question: anyone can comment on a radius that one might use to impregnate the neck with while glueing in the fretboard?
 

ARandall

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The Bartlett plans show a TR and neck cross section for the vintage straight channel. A very useful resource to have for much more than that too.

Did you do auto-translate for your last question? I'm not sure what you are attempting to ask, but 'impregnate' would not I feel be any logical adjective to use in any step of building a guitar.
 

fatdaddypreacher

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The Bartlett plans show a TR and neck cross section for the vintage straight channel. A very useful resource to have for much more than that too.

Did you do auto-translate for your last question? I'm not sure what you are attempting to ask, but 'impregnate' would not I feel be any logical adjective to use in any step of building a guitar.
gotta tell ya...you had me laughing out loud
 

valvetoneman

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The Bartlett plans show a TR and neck cross section for the vintage straight channel. A very useful resource to have for much more than that too.

Did you do auto-translate for your last question? I'm not sure what you are attempting to ask, but 'impregnate' would not I feel be any logical adjective to use in any step of building a guitar.

Depends how the Mrs is dressed whilst building said guitar
 

mistermikev

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The Bartlett plans show a TR and neck cross section for the vintage straight channel. A very useful resource to have for much more than that too.

Did you do auto-translate for your last question? I'm not sure what you are attempting to ask, but 'impregnate' would not I feel be any logical adjective to use in any step of building a guitar.
you know i was on the site earlier about to pull the trigger but it's a hardcopy. I get why they don't want to release digital... but I'd basically have to scan it in to really work with it the way I like to. I don't want to hang on to some big paper doc. further... I'm not all that interested in getting the EXACT placement of control cavity or wire trench. Respect to the folks that do that sort of thing but I'm really not that interested in the irrelevant minutia.

impregnate can mean a lot of things other than getting a lady pregnant, but the jist of that is that something is put into her that becomes a part of her.
fair enough, it is a liberal use of the term but the basic idea is we IMPRINT (there is that better?) a curve into the neck/fretboard. We embue a fretboard with releif. we force a curve onto the fretboard.

This isn't something necc done by gibson afa I know... but I am aware that bartlet sells a piece of wood with a curve on it that would be used to clamp to the neck/fretboard to conform it to a curve. I am aware some other builders do this as well and am just curious if anyone happnens to know what radius would be used if one were to do that.
 

Joe Desperado

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To impart a curve/relief into a fretboard can be done in two ways.

To clamp a bit of relief can be done with a caul (Bartlett) or by pressing the backside of the headstock up. (See stewmac videos). Not more then .015-.020 of relief.

second is to glue it flat, Once dry, crank the truss rod to cause a .020 back bow and then use a radius block to sand it flat (before frets go in)
 

mistermikev

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To impart a curve/relief into a fretboard can be done in two ways.

To clamp a bit of relief can be done with a caul (Bartlett) or by pressing the backside of the headstock up. (See stewmac videos). Not more then .015-.020 of relief.

second is to glue it flat, Once dry, crank the truss rod to cause a .020 back bow and then use a radius block to sand it flat (before frets go in)
thank you Joe. .015-.020 - that's a number i can work with. I very much appreciate the reply and info.

find a radius that changes .020 over the fretboard length and I can mill it in, or as you mentioned put pressure on headstock, or cut a caul that will produce that relief. very much appreciate the info. I would have guessed it would be in the neighborhood of typical string relief but I suppose beending .078" in might take some real pressure and not leave much room for mistakes.

that's an interesting take I have not heard - using a sanding block to create the relief in the fretboard... clever. I'd like to avoid any hard work so not sure I'd go that method but it's a good trick to know all the sm and I thank you for telling me.
 

cmjohnson

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If the neck is dead straight, and the fretboard is dead straight when you make the neck, then all the relief you need should be adjusted into the neck just by truss rod adjustment. I have never seen a case where it was necessary to carve relief into a properly made neck.

If fall-away over the last few frets is required, and sometimes it is and sometimes it isn't and after 36 years as a guitar tech and builder, I still can't quite put my finger on why fall-away is needed on some necks and not on others, then I dress the fall-away into the fingerboard itself and don't want to grind fall-away into the frets as this can result in low frets that make it harder to play, where it's already harder to play.

When in doubt, I counsel you to refer to the way PRS makes their necks. And whether you're a fan of PRS guitars or not, nobody really argues that they don't have the most consistent and stable necks in the business. Their whole neck production process is built around assured stability. They let the neck relax and assume its most stable shape after EVERY process in its manufacture, and that takes a month, while their bodies go through production in two days.
 

mistermikev

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If the neck is dead straight, and the fretboard is dead straight when you make the neck, then all the relief you need should be adjusted into the neck just by truss rod adjustment. I have never seen a case where it was necessary to carve relief into a properly made neck.

If fall-away over the last few frets is required, and sometimes it is and sometimes it isn't and after 36 years as a guitar tech and builder, I still can't quite put my finger on why fall-away is needed on some necks and not on others, then I dress the fall-away into the fingerboard itself and don't want to grind fall-away into the frets as this can result in low frets that make it harder to play, where it's already harder to play.

When in doubt, I counsel you to refer to the way PRS makes their necks. And whether you're a fan of PRS guitars or not, nobody really argues that they don't have the most consistent and stable necks in the business. Their whole neck production process is built around assured stability. They let the neck relax and assume its most stable shape after EVERY process in its manufacture, and that takes a month, while their bodies go through production in two days.

thanks for the thoughful reply, i very much appreciate.

my last neck had .082mm action on the high e with zero buzz unless I bent a full step, and 1.19mm on the low e (dbl action truss)... so I'm confident in my ability to build a neck with good action, but this excercise is about more than that. It's about studying other ways to do it and not assuming that I know a better way.

needed or not - clearly folks do builds w/o it so it is in fact not needed (agreed)... but a few people I respect have mentioned that they do it so... perhaps there is something there for me to learn.

I can't tell if you are mentioning fall away because it's on topic... or an unrelated point... but to me it seems an unrelated point. As I understand, and please y'all correct if I'm wrong, the idea is to engineer in some back bow and effectively give yourself the effect of a two way truss rod with a single rod... so that when you loosen it all the way it actually bows backwards out of relief just a hair (probably actually wouldn't actually bend backward with string tension on but it might go perfectly straight). I am not aware if anyone is doing that for the purpose of putting in fall away and if I'm wrong i'd like to know. would seem counter-intuitive as I would normally get the frets perfectly straight first step... and that would eliminate any fall away introduced by the whole process.
 

CB91710

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Here's a Fender Bi-Flex.


Truss-Rod-Blue-Print-Full.jpg
 

mistermikev

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Here's a Fender Bi-Flex.


View attachment 575745
thank you and thank you for the reply, that's one I have not seen before and is a nice doc. can def use that and am adding it to my stash of info. that said... it's quite a dif rod... so would still love to see equivalent for a lp if it's out there and anyone could rub my nose in it.
 

cmjohnson

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Do not build a neck with built-in back bow because if you get it wrong and the neck is too stiff for string tension to bend the neck enough to make the action right, you have literally wasted the effort to make the neck.

I have one neck that ended up with a hair of backbow. I got VERY lucky that string tension balanced it, but only with a .010-.046 set of strings....at first. As that guitar is now 35 years old, it has relaxed a little bit and now it'll assume perfect low action even if I use .008s But it was a very close call.

If you want the lowest possible buzz free action across the board, it's very relevant to talk about fall-away as much as it is to talk about relief. You might end up with a neck that won't play clean above the 16th fret even though it's perfect up to that point, and that is when fall-away will be needed.

The last strat I refretted had never played clean in the heel area. It needed some fall-away and I carved some into the board, and that made it perfect. The owner is thrilled. Finally he can play clean on the heel area.

If you want the best possible action, you can't ignore ANY factor that affects it. Nut cut, bridge cut, fretwork, relief, fall-away, they all matter. You have to look at the whole picture and address each part of it to your full ability.

As for truss rods, any type that works....works., Personally I use the PRS style double action single rod, which works on the turnbuckle principle. Yes it is installed in a slightly curved channel with a curved filler laid over it. I cut the curved channel via
a milling machine (knee mill) with the neck supported in the middle and bent hard with clamps to force it into a shape whereby
the cutter cuts a straight path, and when the clamps are released, the neck returns to straight with a curved truss rod channel
in it. No worries about the neck breaking, If THAT will break or crack it, it wasn't a good enough piece of wood to use for a neck anyway.
 

LtDave32

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I've searched over the years for a bi-flex style truss rod made aftermarket by anyone.

No such luck as of yet.
 

CB91710

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I've searched over the years for a bi-flex style truss rod made aftermarket by anyone.

No such luck as of yet.
Only thing I am aware of are the two-way units like those sold by SM that have a piece of barstock connecting the end fittings.
Their advantage is they don't require any kind of anchor on the buried end.
I think the Fender Bi-Flex is unique... probably patented.

Would be pretty easy to DIY something like this, but that would take a deep channel.

DIY2-Way.jpg
 

cmjohnson

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What makes Fender's Bi-flex truss rod work is the fact that the adjustment end of the rod is capped by a plug (walnut in Fender's case) that holds the adjustment nut in a fixed position. When adjusted for backbow, the nut wants to push out of the top of the headstock but the plug blocks its movement. If you were to have the plug pop out you'd have a single action truss rod. It's the plug that makes it work in both directions. Simple but very clever.

The anchor under the 7th fret dot inlay serves just to constrain the truss rod so it doesn't blow out the walnut spline.

One nice thing about the biflex truss rod is that the rod itself does not rotate in the neck.

The PRS type truss rod I use requires the rod to turn in the neck when being adjusted, and this means that the rod must be sleeved and permanently lubricated (with grease) so as to avoid it freezing into the wood if it gets ANY rust on it.
 

mistermikev

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Do not build a neck with built-in back bow because if you get it wrong and the neck is too stiff for string tension to bend the neck enough to make the action right, you have literally wasted the effort to make the neck.

I have one neck that ended up with a hair of backbow. I got VERY lucky that string tension balanced it, but only with a .010-.046 set of strings....at first. As that guitar is now 35 years old, it has relaxed a little bit and now it'll assume perfect low action even if I use .008s But it was a very close call.

If you want the lowest possible buzz free action across the board, it's very relevant to talk about fall-away as much as it is to talk about relief. You might end up with a neck that won't play clean above the 16th fret even though it's perfect up to that point, and that is when fall-away will be needed.

The last strat I refretted had never played clean in the heel area. It needed some fall-away and I carved some into the board, and that made it perfect. The owner is thrilled. Finally he can play clean on the heel area.

If you want the best possible action, you can't ignore ANY factor that affects it. Nut cut, bridge cut, fretwork, relief, fall-away, they all matter. You have to look at the whole picture and address each part of it to your full ability.

As for truss rods, any type that works....works., Personally I use the PRS style double action single rod, which works on the turnbuckle principle. Yes it is installed in a slightly curved channel with a curved filler laid over it. I cut the curved channel via
a milling machine (knee mill) with the neck supported in the middle and bent hard with clamps to force it into a shape whereby
the cutter cuts a straight path, and when the clamps are released, the neck returns to straight with a curved truss rod channel
in it. No worries about the neck breaking, If THAT will break or crack it, it wasn't a good enough piece of wood to use for a neck anyway.
thanks for the reply. I would think going with a .015 difference... would be pretty safe. if I end up with a neck that doesn't work... well then I'll learn something about steaming off a neck!!
I've put fall away into every neck I've built assuming they all can benefit. I like super low action, as I mentioned above, .082mm on the high e... was lovely. I'm certain I only achieved that with fall away. my typical action is going to have a small amount of string buzz if you play really hard - and that is where fall away helps a lot.

best possible action - well I'm not new to setting up guitars... have been doing it myself for 20+ years and I wouldn't say "professionally" but I did do it at a music store for a few years and did it on multiple partscasters I've built before getting into scratch builds. had done some fret leveling but really only did my first refret about 9 guitars ago.
regarding nut... well when I first started out I'd always try to get the nut the lowest possible and then set action. I've learned over the years that if you set the nut a little bit higher... you can highlight an area of the neck. with a higher nut, you get a slightly higher action at the 1-7... but you get a sweet spot around 12-17 where action is a bit lower. or you can set the nut super low and get your best action right at 1-7... and all kinds of variation between.

truss rods - well I like the allied luthier truss and pretty much have used those and they are fantastic. lighter, better made, turn super easy... but I believe there are likely multiple "bests" here. a rod style is going to require a smaller trench, is lighter still, and occupy's a area of 'best' all it's own. again, for me, this is about "studying the greats" and learning something. I know I can make a rock solid neck with an allied dbl action truss... and that would be the safe bet afa building a neck... but knowing how to do either and having had the experience at the least will fill out my ideas of why one might be better than the other.
 

mistermikev

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thank you @cmjohnson for mentioning the prs style rods... I'm storing that in the back of my mind for when I get around to studying the custom 24!! at that point you will likely find me back in here asking for pics/advice and I hope you'll be as apt to chime in. right now my brain isn't quite ready to take in how that rod works... one track mind I guess... full disclosure I wasn't aware at all that there was anything different about the prs style rod until you mentioned it. thank you for bringing it up.
 

cmjohnson

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I make my own PRS style rods . (OK, I have a machine do the work...but it's to my specs. specs derived from extracting the rod from an actual PRS scrap neck I got from someone who used to work at PRS.

It is a turnbuckle.

The rod is threaded at both ends. One end is threaded left handed. The other is threaded right handed.

Flat steel rectangular washers that are drilled and tapped (one left handed, one right) are screwed onto the rod. At this point, the adjuster nut is WELDED to the nut end of the rod. I don't recall at this moment if the nut goes on the left handed or the right handed end. It will affect whether or not the rod works in the normal mode (clockwise to tighten) or in reverse.

Because the rod is buried deeper into the body end than the headstock end, the flat nut that is at the body end of the rod is a little larger.

The two flat nuts fit into tightly machined slots in the neck.

The rod is positioned for easy access to the adjuster nut, which will rotate, of course, but won't move in and out.

As for nut slot height, the nut is no longer a factor once you press any string to the fret, so an ideal nut is the same height as a zero fret. To have the height any higher than that just increases action height, particularly up close to the headstock. So I try to get close to zero fret nut slot height. But it can be tricky. One too many strokes with the nut file and you've got an open string buzz and that's just a FAIL.
 

mistermikev

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I make my own PRS style rods . (OK, I have a machine do the work...but it's to my specs. specs derived from extracting the rod from an actual PRS scrap neck I got from someone who used to work at PRS.

It is a turnbuckle.

The rod is threaded at both ends. One end is threaded left handed. The other is threaded right handed.

Flat steel rectangular washers that are drilled and tapped (one left handed, one right) are screwed onto the rod. At this point, the adjuster nut is WELDED to the nut end of the rod. I don't recall at this moment if the nut goes on the left handed or the right handed end. It will affect whether or not the rod works in the normal mode (clockwise to tighten) or in reverse.

Because the rod is buried deeper into the body end than the headstock end, the flat nut that is at the body end of the rod is a little larger.

The two flat nuts fit into tightly machined slots in the neck.

The rod is positioned for easy access to the adjuster nut, which will rotate, of course, but won't move in and out.

As for nut slot height, the nut is no longer a factor once you press any string to the fret, so an ideal nut is the same height as a zero fret. To have the height any higher than that just increases action height, particularly up close to the headstock. So I try to get close to zero fret nut slot height. But it can be tricky. One too many strokes with the nut file and you've got an open string buzz and that's just a FAIL.
would love to see a pic if it's not too much trouble... I appreciate the detailed info.

afa nut... I have def gone one stroke over the line b4 hehe.

you know it's hard to argue with that logic... (that the nut doesn't matter once you are fretting a note)... that said I would swear to jeebus I have experienced this. it is really the first and last frets we are focusing on when setting the bridge. I guess perhaps b4 I was cutting the nut in a way that you might call "too low"... but I have cut it that low and it doesn't buzz on the first fret (nor any)... so is that really 'too low'? not necc. because the bridge end is raised enough to compensate just enough for that open string to ring free over the first. Finding that... I have stopped myself a little earlier in cutting the nut... and found that it allows me to set the bridge side lower than I would have. Either way is going to be out of the equation once you are fretting... yet one way 'feels' lower at the 12+ while the other way 'feels' lower at the 1-7. granted, I'm probably not explaining this well and we are also talking about a difference so slight that it would be damn near impossible to measure.
 

LtDave32

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would love to see a pic if it's not too much trouble... I appreciate the detailed info.

afa nut... I have def gone one stroke over the line b4 hehe.

you know it's hard to argue with that logic... (that the nut doesn't matter once you are fretting a note)... that said I would swear to jeebus I have experienced this. it is really the first and last frets we are focusing on when setting the bridge. I guess perhaps b4 I was cutting the nut in a way that you might call "too low"... but I have cut it that low and it doesn't buzz on the first fret (nor any)... so is that really 'too low'? not necc. because the bridge end is raised enough to compensate just enough for that open string to ring free over the first. Finding that... I have stopped myself a little earlier in cutting the nut... and found that it allows me to set the bridge side lower than I would have. Either way is going to be out of the equation once you are fretting... yet one way 'feels' lower at the 12+ while the other way 'feels' lower at the 1-7. granted, I'm probably not explaining this well and we are also talking about a difference so slight that it would be damn near impossible to measure.

Not as impossible to understand as you might think.

I've mocked-up the action on several guitars in-process of building. I set a nut at the end of the fret board, used an elastic string all the way to the bridge, then fretted the string at the first fret. The whole action lowered by a significant amount.

With angles, a little at the start (nut or first fret) vectors into a lot at the other end.

I shoot for "two business cad" depth from the bottom of the string to the top of the first fret, or .013-.018 between them.

That's what I call "low, but not buzzy".

I take a lot of time in setting this stuff up. Ideally, I want my bridge to be on the deck and the strings just touching the 22nd fret. I don't favor high-in-the-sky bridges.

A forum member here sent me his SG for a neck reset. That thing had a neck angle of 4.55 degrees! That's no lie.

WAY too high. This is from the factory. 2013 SG. The bridge pup was practically out of it's ring to get high enough to the strings. Bridge was way jacked-up to get the strings to clear. IT was like playing a damn cello.

This was NOT right. No way. So I pulled the neck, repaired the angle to give it 2.5 degrees.

All worked out perfect after that.
 

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