String radius question

[buckethead bungler]

I just bought myself a shiny new set of string radius gauges from Stew Mac and was wondering what radius I should set my strings at given that Jackson fretboards have a compound radius of 12 to 16". Do I take an average and set it at 14" or do I set it to either extreme of 12" or 16"?

[Chad]

I'd say it's personal preference, but I'd probably go with the 16".....I'd rather have the action lower for the upper frets than the lower frets. Or you could could compromise at 14".

[Spivonious]

This thread confuses me.

[Sunbane]

I'm thinking something like 17" or 18" would make the best match if you want it to match the fretboard all the way? Just theorizing here - I've never bothered with getting the radius accurate myself, but maybe I should look into it...

[slash]

Are you trying to adjust the radius at the bridge?

[Chad]

This thread confuses me.

I've found that the easiest way to get a grasp on this is to do a few exaggerated drawings on paper. For a flat radius use a straight line, which represents the frets, then draw a flat line above, which represents a simulation of string radius....the action will be even across all of the strings.

Now draw another straight line, then draw an upside down kind of "u" shape over the flat line. This will simulate a less flat string radius. Notice how the inner strings are gonna have higher action compared to the E strings?

Do a few other pics and you can get an easy grasp of what is going on.

[Chad]

Are you trying to adjust the radius at the bridge?

Yeah, good question. If you have a Floyd and have to use shims this can be quite the process.

[ihocky2]

You should set the bridge radius to match or be slightly flatter than the fretboard at the bridge end. So if fret 22 measures 16" radius, then set your bridge to that. And then if you have the tools, cut the nut slots to match the head end radius. If you have a locking nut, it "should" match the radius already. Now your stings will follow the contour of the fretboard. If you don't have the tools to file the nut slots, then just let them as they are. Even though once again they "should" be at the same radius as the fretboard from the factory.

[Spivonious]

I've found that the easiest way to get a grasp on this is to do a few exaggerated drawings on paper. For a flat radius use a straight line, which represents the frets, then draw a flat line above, which represents a simulation of string radius....the action will be even across all of the strings.

Now draw another straight line, then draw an upside down kind of "u" shape over the flat line. This will simulate a less flat string radius. Notice how the inner strings are gonna have higher action compared to the E strings?

Do a few other pics and you can get an easy grasp of what is going on.

Oh I knew what the fretboard radius was...I guess I just never thought of adjusting the bridge saddles to match. That's what you get with Floyds I guess.

The whole "string radius" term is what confused me. I think "bridge radius" would make more sense.

[dg]

I agree with what Sunbane & ihocky2 said. Picture a compound radius fretboard as a section of the surface of a cone, just like in this Charvel ad:

http://www.audiozone.dk/CatalogScans/Ch1988Imports/pages/Ch1988ImportsPage01.htm

To keep the strings following that arrangement, the radius should be greater at the bridge than at the 22nd fret. Using a little rough math here, the radius increases by 4" over the ~18 1/4" from the nut to the 22nd fret, or about .219" of increase in radius per inch up the fretboard. 7 1/4 inches more to the bridge adds a little more than 1.5" of radius, for about 17.5".

Great on paper, but the bottom line is you still just have to go by what the strings do in the real world. I usually end up with my bridge set a little higher on the low E side, and sometimes need a little extra shimming (or raising of the saddles on a Kahler), usually D & G saddles.

[buckethead bungler]

Thanks for the help guys. A mate of mine calculated that it needs to be exactly 17.6923180443" at the bridge, but unfortunately the Stew Mac tools jump straight from 16" to 20".

I know the guitar "should" be factory set to match the radius though I just bought myself a brand new Kahler bridge to replace the old one in my late 80s Jackson and am in the process of setting it up.