fingerboard radius vs nut radius

[hittitewarrior]

Can I use a 7.25 radius nut with a 12" radius fretboard?  What is the impact in playability... Middle strings will be higher off the fretboard... Noticeable enough not to recommend?

Any guidelines as far as how far away from matching they can be?

 

Thanks!

[curtisa]

Radius difference is too great. If you tweak the nut height such that the outer strings are at a correct height, the inner strings will be far too high.  You'll find that intonation in the first few frets will be massively sharp and playability will feel pretty bad.

I've personally never gone more than 2" difference between nut radius and fretboard radius, and that was only because I couldn't practically adjust the depth of the nut slots (10" radius Floyd Rose locking nut on a 12" radius board).

You're better off re-cutting the nut slots so that they match the radius of the board (or buying the correct nut), or re-radiusing the board to match the nut.

[hittitewarrior]

Ok thanks, good to know.  I was trying to avoid buying all the nut files/saw/etc. at this time, but maybe thats the better option.

How about a zero fret?  If I understand correctly, the only thing the nut is htere for on those is to keep the strings in place, not as a contact point.  Perhaps the "cheaper" solution...  how do they sound?

[curtisa]

19 minutes ago, hittitewarrior said:

How about a zero fret?  If I understand correctly, the only thing the nut is htere for on those is to keep the strings in place, not as a contact point.

Correct. Provided the slots are deep enough on your 7.5" radius nut you can use it simply for its string spacing without having to cut anything further. Just make sure you allow for the extra real estate behind the zero fret to mount the nut.

 

21 minutes ago, hittitewarrior said:

how do they sound?

I have no personal experience, but by all accounts it's not unlike the sound of the equivalent fretted strings. Some people claim that intonation in the first few frets is improved compared to a regular nut, as the zero fret is levelled to be the same height as all the other frets on the neck (although a properly cut nut should have the same effect).