Compound radius question.

[warlok]

With a compound radius (say 12"-16"), is it a 12' radius up to a certain fret and then 16" from there? Or is it a gradual widening of the radius down the neck?

[MakeAJazzNoiseHere]

Gradual flattening. It's a conical shape.

[Spivonious]

^yep. Imagine they took an ice cream cone and chopped it in half.

So the first fret is 12", second fret is 12.2", third fret 12.4", .... , 22nd fret 15.6", 23rd fret 15.8", 24th fret 16".

This also means that the radius at the bridge is actually around 20".

[Tim_B]

sorry for semi-hijacking this thread ... but what might you want to take into account about the profile of a bridge or trem in regard to matching it to a neck profile?

[atdguitars]

The bridge profile is key to the whole guitar setup. If the bridge won't make the same, or close to the same, radius as the neck then you probably won't get the most playability from the guitar. Most bridges can be made to do what you need it's just some will require more shimming or milling than others.

[Grandturk]

This also means that the radius at the bridge is actually around 20".

Well, to be accurate - you would say that if the fretboard continued to the the bridge, the radius would be around 20".

The radius of the strings is only going to follow the radius of the fretboard if the bridge is setup similarly to what the fretboard would be - as discussed above.

In my experience, not sure if this needs to be done to have a good playing guitar.

[MakeAJazzNoiseHere]

I have several 12-16" compound necks (Charvel & Jackson) with Floyds. Some of them are the basic "Floyd without the stock shim" radius which I believe is close to a 16", and others I've shimmed to 20" using Allparts shims.

SL2H Pro archtop = shimmed
SD/CS Charvel mutt = shimmed
DK1 = shimmed
SL2 = not shimmed (I replaced the JT580LP with a Floyd & didn't shim it)
SL1 = not shimmed (stock)

The relative action on the outside strings being the same, the center strings are closer when the bridge is shimmed. And I basically set them so the high E string is the same height either way (about 1.7 mm.)

The feel is a little flatter, but honestly it's not a huge difference and I can jump from one to the other without any difficulty. I'm glad that I tried it and I wouldn't pull the shims from the ones I've done but I'm in no hurry to shim any of the ones that aren't, if that tells you anything.

[warlok]

OK. So how do you level the frets. I've heard people say that "frets have been leveled and crowned". I know how for something like a strat or anything with a constant radius but how do you "level" a compound radius? How is it done? Seems it would be easier to re-fret than fix. I can see filing and crowning 1 or 2 frets out of whack but more than that??

[MakeAJazzNoiseHere]

It's not that hard to do a reasonable job of leveling a compound fretboard. I don't think most guys who do that stuff for a living use the "radiused blocks" to level the straight radius stuff, so there's a litle "art" to it in any case.

I use a long beam with 320-grit stick-on sandpaper to level them. I mark the tops fo the frets with a Sharpie so I can see what the heck is going on, first, and you also need to get the neck perfectly flat (or as close as possible.)

Anyway what's different with compound radius is as I move it from the nut to the bridge to sand and take material off (I only move it about 1/2") to level, I sweep it across the neck, and follow the path the strings take.

It's hard to explain but you get the beam following the same path the E string would take, and it's at a slight angle. As you move it slightly back and forth nut to bridge, you also move across the neck slowly, moving the bridge end a little faster than the nut end, so say the bridge end moves 3" and the nut end moves 2" when you've made one pass across.

[warlok]

Ah. I get it. That must take alot more patience and practice than a straight radius. As a newbie to fretwork, I'll stick to the straight radius with a radius block for now. Thanks.

[MakeAJazzNoiseHere]

Oh, I'm not particularly experienced with fretwork as far as I'm concerned. I'm not a luthier, just a hobbyist.

I had done straight radius before with a flat block but the compound radius thing scared me, too. I just had one that I "couldn't make worse" and so I wanted to try it. It came out great!

[Grandturk]

Oh, I'm not particularly experienced with fretwork as far as I'm concerned. I'm not a luthier, just a hobbyist.

And I was going to ask you to do my Model 4. You just lost yourself some money!

[MakeAJazzNoiseHere]

I did my DK1 a couple of weeks ago, so I guess I'm getting braver. But I'm only willing to take a chance on ruining my own stuff at this point.