Question about string-spacing and Jackson Tune-O-Matics

[DonP]

I personally think the bridge should match the radius of the fretboard closest to the bridge.

Lets think about this. If you have a 12" radius bridge with a 16" fretboard, the middle strings would be too high or the outside E's would be too low.

I'm pretty sure when I took my 1996 Classic Premium Plus to Dan Erlewine for a new bridge, he made the radius match the fretboard by the bridge.

[leftykingv2]

I personally think the bridge should match the radius of the fretboard closest to the bridge.

Lets think about this. If you have a 12" radius bridge with a 16" fretboard, the middle strings would be too high or the outside E's would be too low.

I'm pretty sure when I took my 1996 Classic Premium Plus to Dan Erlewine for a new bridge, he made the radius match the fretboard by the bridge.

I am posting the email from my friend Bradley who works for FMIC.

[leftykingv2]

Bradley Shelton <[email protected]>	Oct 23 (7 days ago)
to me

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Hey Stephen,

I just got word back from my Jackson guy that the bridge’s radius always mirrors the radius at the nut. So for a 10-14 compensated radius, the bridge radius will be 10”. I hope this helps man, give me a call if there is anything else you need.


Bradley Shelton
Fender Musical Instruments
Consumer Relations
17600 N. Perimeter Drive, Suite 100
Scottsdale,AZ 85255
Ph: 480-845-5132



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[DonP]

And think about an extreme compound radius of say 7 1/2" to 16". Would you really want the bridge radius to be the same as the nut?

That would be .... nuts!

[leftykingv2]

I know DonP I thought the same thing. I am wondering how the 16" part of the radius works on a 12" bridge? It seems like it would be way too wide but they say it works like that somehow. I am just as clueless as you but I am not going to argue with someone who is employed by the company. It is crazy!

[Munkipuss]

A compound radius fretboard takes the shape of a section of a cone. The nut is nearer to the point than the 24th fret. The further you move away from the point, the larger the radius is. As the bridge is further away from the point than the 24th fret, the bridge should logically have a larger radius than both the nut and the 24th fret. Matching the radius of the bridge to the nut doesn't make much sense, unless the fretboard is non-compound.

[leftykingv2]

A compound radius fretboard takes the shape of a section of a cone. The further you move away from the point, the larger the radius is. As the bridge is further away from the point than the 24th fret, the bridge should logically have a larger radius than both the nut and the 24th fret. Matching the radius of the bridge to the nut doesn't make much sense, unless the fretboard is non-compound.

What you're speaking of is known as a C.C.C.R. A "Conical Compensated Compound Radius." which Jackson doesn't do on any standard model. This means that the back shape of the neck is compound as well as the fret board. Only Jackson's Fret boards are compound radius. Not their necks. Each neck has it's own individual back shape as listed in the custom shop build sheet. I honestly don't know how you can sit here and argue with an email that came directly from the company either? I'll say it again for the cheap seats my friend Bradley has worked for FMIC for 14 years and you think you know better? C'mon man!

[Munkipuss]

What you're speaking of is known as a C.C.C.R. A "Conical Compensated Compound Radius." which Jackson doesn't do on any standard model. This means that the back shape of the neck is compound as well as the fret board. Only Jackson's Fret boards are compound radius. Not their necks. Each neck has it's own individual back shape as listed in the custom shop build sheet. I honestly don't know how you can sit here and argue with an email that came directly from the company either? I'll say it again for the cheap seats my friend Bradley has worked for FMIC for 14 years and you think you know better? C'mon man!

I haven't mentioned the back shape at all. All I'm talking about is the shape of the fretboard and its relationship to the radius at the bridge. I don't understand how the back shape of the neck has an affect on any of this. I'd be really interested if you could explain it.

Here's an article that explains a compound radius fretboard, as I understand it, for anyone else that's interested:

http://www.stewmac.com/freeinfo/Neck_relief,_building_and_repair/a-compoundradius.html

It actually has a formula which describes how to calculate the radius at any point on the fretboard.

[Cliff]

I find this odd too - I'd definitely expect the bridge radius to be larger than the nut for a compound radius fretboard - so far as possible you want to keep the string height the same along the length of the fretboard, right? In fact, it's not uncommon to shim a floyd rose bridge to match.

[Grawnday]

I remember someone theorizing on here in a post about correct Floyd saddle radius - that the radius at the bridge is approaching 18". Made sense to me. More sense than 12, 14,15 or 16.

When Jackson mentions a TOM "compensated bridge" in their specs, that's what I thought they meant; "compensated" to match their conical fretboard.

[Chad]

Regardless of the stock radius a bridge has, a file can modify it to get where you want to go.

[leftykingv2]

I find it strange as well. In my opinion a bridge on a guitar with a compound radius of 12" to 16" you would want the bridge to be the same as the biggest part of said radius so 16" makes more sense to me as well from a machinist point of view. I can only tell you guys what my friend said. If he is right or not is up for debate. I don't know either way but if I had to guess from my own knowledge of math I would say 16" sounds closer in my opinion. But again Bradley works for them so who am I to argue? Also +1 to Chad and +1 Munkipuss for the article. Very good article bro!

[leftykingv2]

I haven't mentioned the back shape at all. All I'm talking about is the shape of the fretboard and its relationship to the radius at the bridge. I don't understand how the back shape of the neck has an affect on any of this. I'd be really interested if you could explain it.

Here's an article that explains a compound radius fretboard, as I understand it, for anyone else that's interested:

http://www.stewmac.com/freeinfo/Neck_relief,_building_and_repair/a-compoundradius.html

It actually has a formula which describes how to calculate the radius at any point on the fretboard.

A "C.C.C.R." or a Conical compensated compound radius Means the back of the neck is compound radius as well as the fret board from my understanding. I may be wrong and if you know better I am all ears because we're all here to discuss and learn from each other.

[Munkipuss]

The back of the neck can take many shapes... "C", "D", "U", "V" etc. It's not unheard of for a neck to start at the nut with one shape, and change to another further up the neck.

I don't think the term "radius" applies to neck back shapes however, as they do not exactly follow the shape of a circle, as a fretboard does. I certainly have never heard it used in reference to a back shape.

Perhaps the nearest neck shape to a circle would be a "C", but I don't think even that is fully circular. Just more circular than the others. There is certainly no mathematical reason why a back shape should be circular. Obviously with a fretboard, it does need to be either circular or fully flat to fulfill its function. Bending on a faceted fretboard wouldn't really work.

[toejam]

I don't think the term "radius" applies to neck back shapes however, as they do not exactly follow the shape of a circle, as a fretboard does. I certainly have never heard it used in reference to a back shape.

You are correct. The radius is only for the fretboard.