Compound radius neck: Setting the bridge radius...

[RockStarNick]

Compound radius neck: 10" - 16"

Do I set the bridge radius to match the NUT, or the 22nd fret?

[Ron Thorn]

More like a 20"

[GuitslingerTim]

Compound radius neck: 10" - 16"

Do I set the bridge radius to match the NUT, or the 22nd fret?

Set it to match the last fret, more or less--most people like the strings to graduate in height, starting with the first string.

[Rosewood]

Ron is right, it would be more like 20 if it's 15 or 16 at the last fret, at least that's the way I set it.

[JimiB]

Ron or Rosewood would you expound on the theory here?

[David Collins]

Most compound boards aren't truly a cone, but it's easier to think of it that way for practical purposes anyhow. In an ideal cone the difference will be just as much from the nut to 12th as the 12th to the saddle. i.e., 12" @nut, 16" @12th, 20 @saddle. Real world compounds coincide with a true cone section only rarely. If you have a 12" radius at the nut, 16 at the end, and the frets happen to be properly dressed straight under each string, those will be the only two radii on or beyond the board. The rest would actually be a slightly parabolic shape as opposed to a true radius.

In short, there's no need to ask what radius to set the saddle at. Set the strings to a consistent increase in height (for the most part) from the high string to the low. Don't look at a radius gauge at the saddles - it's a quick tool for roughing in a setup, but more of a crutch when it comes to fine tuning. Use measurements of clearance above the frets - that's what matters. Kind of a "self-leveling" sort of procedure, if you will.

Edit: And yes, as Ron and Rosewood said, the shape will likely end up around 20" (or slightly under in theory, though for all practical purposes saying 20" is good enough).

[Supasso]

Compound radius neck: 10" - 16"

Do I set the bridge radius to match the NUT, or the 22nd fret?
Neither. It should be flatter than both. Try imagine it as a section of a cone. The radius will gradually become flatter from nut to the bridge. The radius at the 22nd fret is somewhere in between. It should be around 20" as Ron said.

[RockStarNick]

Thanks guys.... I'm going to give it a good setup tonight and let you know.

[empty71]

I usually set the radius at the last fret and if it's a compound radius, I set it to the faltter radius :)

[GuitslingerTim]

Okay, I'm setting up a guitar with a compound radius fingerboard of 10"-16", here's the math as I see it:

Length of the fingerboard from the nut to the last fret is 18.25". The offset between the smallest and largest radii of the fingerboard is six inches: 16 - 10 = 6. By dividing the actual length of the fingerboard by the offset of the radii shows how often the fingerboard increases one inch in radius for a given linear length of fingerboard: 18.25 / 6 = 3.04", which means the fingerboard radius increases an inch for every three linear inches of fingerboard.

To calculate the bridge saddle radius, the length of the cone/fingerboard must be extended mathematically to equal the scale length of the guitar, which in this case is 25.5 - 18.25 = 7.25". By dividing the imaginary fingerboard extension by 3.04, the offset that needs to be added to the largest radius of the fingerboard is determined: 7.25" / 3.04" = 2.38: 16 + 2.38 = 18.38". The radius of the saddles should be around 18.3 inches.

Anything wrong with those numbers?

I still fail to see why the action can't be set at the last fret (or any other fret), with every string set to a desired height from the fret used. I like my action 5/64" at the 6th string, and 3/64" at the first, with each string slightly higher than the one before it.

[Soapbarstrat]

I still fail to see why the action can't be set at the last fret (or any other fret), with every string set to a desired height from the fret used.

It certainly can be done that way. Just as good as any other way.

[David Collins]

I still fail to see why the action can't be set at the last fret (or any other fret), with every string set to a desired height from the fret used. I like my action 5/64" at the 6th string, and 3/64" at the first, with each string slightly higher than the one before it.

That's exactly how any board - compound or not - should be adjusted in my opinion, as I mentioned above.

Using a radius gauge to set saddles is kind of like setting up your table saw blade parallel to the wall of your shop. Set up on any tool or instrument is best done by referencing to itself, not introducing completely external reference points like the wall or radius gauge. Find key reference points on the instrument itself (i.e., fret to string distance at a given fret), and adjust to that. Any other method will by nature be less reliable.

As to the math for the board, both standard and compound radiuses can get a bit more complicated. Actually if the frets or board have been shaped or dressed ideally, the final shape of most boards will be neither a tube nor a cone, and would result in only two points from the nut to the saddle where a true radius could actually be found. In the varying board style and shapes, a board could coincide with a conical section and give a constantly increasing radius as you progress down the board, but this is only in a very specific set of circumstances.

If you want more details on fingerboard geometry I'd be happy to oblige, but it probably gets a bit boring.

[daddyo]

Okay, I'm setting up a guitar with a compound radius fingerboard of 10"-16", here's the math as I see it:

Length of the fingerboard from the nut to the last fret is 18.25". The offset between the smallest and largest radii of the fingerboard is six inches: 16 - 10 = 6. By dividing the actual length of the fingerboard by the offset of the radii shows how often the fingerboard increases one inch in radius for a given linear length of fingerboard: 18.25 / 6 = 3.04", which means the fingerboard radius increases an inch for every three linear inches of fingerboard.

To calculate the bridge saddle radius, the length of the cone/fingerboard must be extended mathematically to equal the scale length of the guitar, which in this case is 25.5 - 18.25 = 7.25". By dividing the imaginary fingerboard extension by 3.04, the offset that needs to be added to the largest radius of the fingerboard is determined: 7.25" / 3.04" = 2.38: 16 + 2.38 = 18.38". The radius of the saddles should be around 18.3 inches.

Anything wrong with those numbers?

I still fail to see why the action can't be set at the last fret (or any other fret), with every string set to a desired height from the fret used. I like my action 5/64" at the 6th string, and 3/64" at the first, with each string slightly higher than the one before it.

Agred.
In the real world, you set the action with a steel rule and adjust each saddle individually (Fender style brides). If you had a guitar with a compound radius neck and a TOM style bridge, I'd still file the saddles to achieve the same results. The radius is whatever it is - you don't calculate it.

[RockStarNick]

Math making my brain hurt!!!!

I'm terrible at math. That's why I'm a musician. haha.:rotflmao

I'm gonna measure at the 12th fret.

[Ron Thorn]

You need to know the string spacing at the nut and the string spacing at the bridge to calculate it accurately.

[fullerplast]

We had a cool discussion about this a while back and I think pretty much showed that you need to know at least three variables to define the cone surface. That can be string spacing at the nut and bridge, along with the radius of either, or string spacing and radius at either end and the scale length, etc. We had some formulas worked out but in the end, Vince Cunetto had a cool Excel calculator that made it easy to find what the radius should be at any point on the neck. Just plug in the known values and there you go:

Vince's radius calculator (http://www.vinettoguitars.com/index_files/MiscContent/CunettoFretboardCalculator.xls)

Using this table you can easily see the cone being defined as you move down the neck.

Don't get too anal about it though....the differences are pretty small and ultimately, if you buzz or fret out you're just gonna raise the action a bit anyway.:cool:

[David Collins]

That formula will work fine for a very specific variation of fret board radius, but only for a single set of circumstances within an otherwise infinite window of possible shapes. There is no end need to maintain a constant cone shape as that predicts, other than for it's simplicity of geometric definition or for a simple form of board shaping jig in building. A competent builder or tech can actually use any start and end radius they choose and still create a straight surface under each string. It's just about as easily crafted as a true cone, just not so simply defined by formulas.

In any case, this is all a matter for the builder or tech in shaping a board or dressing the frets. I've created my own pile of formulas related to fret boards, but it's largely academic with little need in real world use.

In the setup process there is no need or benefit to labeling the end radius anyway. It is what it is after saddle heights are determined by string height measurements.

[operanonverba]

David- I use the method you have described to set bridge radius and have always used the 12th fret to measure each string. This works great on my guitars with individual saddles but not so good on my Gibby bridges. On those guitars I just measure and set the bridge height on the E strings. My question is do you reccomend measuring from any other fret besides the 12th?

[David Collins]

My question is do you reccomend measuring from any other fret besides the 12th?

There is no official standard, but 12th fret measurements are the more common and more practical in my opinion. Some measure at the end, but with the different numbers of frets as well as different levels of kick-up or fall-away at an extension, I see this measurement as less reliable.

Of course in final setup there's always the fine-tweaking where numbers are often better thrown to the wind. For communicating your setup preferences to another or recording them for reference though, I think the 12th is a good standard location.

[Soapbarstrat]

If you measure at the 13th, your amp will fall on your guitar.

[RomanS]

Am I the only guy here who sets the height of his bridge saddles by ear rather than by a fixed radius or mathematical formula?

(Meaning that I play each string along its length, then set it lower until it starts buzzing, and raise it a bit from that point again.)

Oh, and BTW, the necks on my two favorite guitars have 10-16" compound radius, too (Warmoth).

[Boris Bubbanov]

Am I the only guy here who sets the height of his bridge saddles by ear rather than by a fixed radius or mathematical formula?

Oh, and BTW, the necks on my two favorite guitars have 10-16" compound radius, too (Warmoth).


I like the intuitive approach as well. Maybe the bridge radius should be 19, but when the wash is folded, it whatever it is. If you play the string and it is too low, raise it.

I like those compound radius necks as well. I just got a VM Boatneck Tele neck in light birdseye from Warmoth that it 1.695 at the nut, as opposed to 1 + 11/16ths, and I'm tickled with it. Can't wait to build it out.

[David Collins]

Am I the only guy here who sets the height of his bridge saddles by ear rather than by a fixed radius or mathematical formula?


That's pretty much what most people agree on, and what I was referring to here -
Of course in final setup there's always the fine-tweaking where numbers are often better thrown to the wind. For communicating your setup preferences to another or recording them for reference though, I think the 12th is a good standard location.

When you fine tune a setup however, it is surprising how close to consistent the measured results end up. This is why it can be beneficial to start from measured distances to quickly put you in the ballpark range. Then you can begin a more delicate dance of fine tuning between the neck and saddle adjustments. And even if you are fine tuning through feel and sound, I find keeping note of measurements through the process can make things both more efficient and consistent.


a VM Boatneck Tele neck in light birdseye from Warmoth that it 1.695 at the nut, as opposed to 1 + 11/16ths...

For all practical purposes, 1.695" is 1 _ 11/16".

[WahmBoomAh]

Potential hijack here .. but it IS related ...

Is a non compound board (10" for ex.) apt to regulate more evenly up and down the board ?
I`m gonna order a jazz guitar (no major bending to speak of ) and like the 10" curve for sweep picking ... I find a compound radius requires a compromise on action ... the D and G strings seem to be at different heights relative to the fingerboard position .

Is this only in my imagination ?

interesting stuff !

Also ...isn`t a 10-16 compound overkill ? I mean ....can`t you get clean bends with a shallower curve ... maybe 10-13 ????

[WahmBoomAh]

16 months later and I still have the same question !!!

For a setup with minor string bending ... wouldn`t I benefit from no or little compounding of the radius if I wanted uniform LOW action with 12`s (jazz type tension setup) ???

[walterw]

16 months later and I still have the same question !!!

For a setup with minor string bending ... wouldn`t I benefit from no or little compounding of the radius if I wanted uniform LOW action with 12`s (jazz type tension setup) ???no, if anything it would be the opposite, in that a compound board would better follow the narrow nut spacing as it widens towards the bridge.

it's not that you'd benefit from a non-compounded board, it's just that with no bending, you wouldn't be so much hurt by it.

also, with little or no bending, you wouldn't need such a flat radius as most compound boards have anyway.

[WahmBoomAh]

no, if anything it would be the opposite, in that a compound board would better follow the narrow nut spacing as it widens towards the bridge.

it's not that you'd benefit from a non-compounded board, it's just that with no bending, you wouldn't be so much hurt by it.

also, with little or no bending, you wouldn't need such a flat radius as most compound boards have anyway.

thank you , sir .

I like the 9.5 fender radius ... for a small bodied carved archtop w a 25.5 scale ... if you started at 9.5 ... what would be your minimum compounding to make it right for you ?
I don`t like the arch of the strings fluctuating so much up the neck because it`ll affect the right hand position for fast sweep picking .

I`d like the string curve at the bridge to be close to the 9.5 ,,, if it flattens out to much I`ll lose the arch on my picking hand for sweeps . Make sense?

[Rock Johnson]

Wow... a thread where Ron Thorn, David Collins, Boris Bubbanov, Fullerplast, and Walter W. all join in.

I always *think* I know something about setups until I read what you guys have to say.

[Ang3lus]

what do you set the nut with a 10"-16" compound radius
to a 10" or 12"?

[Eagle1]

what do you set the nut with a 10"-16" compound radius
to a 10" or 12"?
Neither ,you set the correct clearance over the first fret as always.

[Ang3lus]

oh i see
thanks.

[khromagi]

go check out the Warmoth boards, lots of info there

[Kingbeegtrs]

Didn't someone drag this subject out a while back?

[GtrDr]

Didn't someone drag this subject out a while back?

It's new to this guy. No biggie Oh, radius gages are good for roughing in, but the string height at the 12th fret & the last fret is the final check. I'm guilty of relying too much on the gages & ignoring an even string height.

[crobar]

I couldn't have said it better..Most compound boards aren't truly a cone, but it's easier to think of it that way for practical purposes anyhow. In an ideal cone the difference will be just as much from the nut to 12th as the 12th to the saddle. i.e., 12" @nut, 16" @12th, 20 @saddle. Real world compounds coincide with a true cone section only rarely. If you have a 12" radius at the nut, 16 at the end, and the frets happen to be properly dressed straight under each string, those will be the only two radii on or beyond the board. The rest would actually be a slightly parabolic shape as opposed to a true radius.

In short, there's no need to ask what radius to set the saddle at. Set the strings to a consistent increase in height (for the most part) from the high string to the low. Don't look at a radius gauge at the saddles - it's a quick tool for roughing in a setup, but more of a crutch when it comes to fine tuning. Use measurements of clearance above the frets - that's what matters. Kind of a "self-leveling" sort of procedure, if you will.

Edit: And yes, as Ron and Rosewood said, the shape will likely end up around 20" (or slightly under in theory, though for all practical purposes saying 20" is good enough).