Flat vs Radius bottom nut

[AVClub]

I am new to building and before tackling an entire build, I am working on a neck for my 70's Musicmaster. I have the template ready to be cut and have done some 3d prints to test dimensions and everything looks good. However, one thing I stumbled upon is radius'd vs flat bottom nuts. What do you use and why? It seems a flat bottom would be much easier for me to cut the slot for in my shop, even if its not period correct (Thats fine by me.) are there any big advantages to the curved bottom nuts? Stopping from movement? It seems with a tight cut slot, glue, and string pressure, the nut would be hard pressed to move. 

[Bizman62]

As a background, I've been participating a wintery "guitar building course" for almost a decade, led by Master Luthier Veijo Rautia. He has cut us several fretboards in his private workshop and the nut slots have always been flat bottomed. Needless to say that the first guitar to build is most often a Strat or Tele.

The only advantage I can figure out for a radiused bottom is to leave more material above the truss rod nut - but that is negated by the hole needed for the notch in the nut!

As you suspect, a tight cut slot and string pressure are enough - many nuts actually sit at the end of the fretboard on the headstock! A tiny dab of glue is needed only to hold the nut in place when the strings are removed for maintenance.

[curtisa]

I believe the curved-bottom nut slot dates from a period in some manufacturer's histories (notably Fender, but maybe some others too) where the fretboard itself was a curved lamination glued to the neck which had the radius already applied to it, and then the fret slots and nut were cut in one operation using a special swinging jig and ganged circular saw blades. The frets themselves would be driven in from the side rather than hammered in from above. As the resulting fret slots would be curved from the ganged saw blades and swinging jig, the nut slot would also be curved so the nut needed to be curved to match.

These days there's probably no real need to do such a complicated series of operations when making a neck except perhaps if you're somehow trying to remain historically accurate. To do this by hand without the aid of jigs is going to be challenging; for that reason alone most people would simply cut the nut slot (and fret slots) flat and use a flat-bottomed nut.

As far as after-market nuts go, you'd probably only purchase a curved nut if the neck you were trying to fit it to already had the curved slot to begin with. This would largely only apply to replacing an existing nut in an old neck.

 

[mistermikev]

i always do flat bottom because it is easy.  I believe there is an argument out there that the advantage of a curved slot nut is that the material under the string is more consistent... but I'm certain this is just legend that sprang up after the fact.  I don't believe fender ever did them curved out of a belief that it sounded dif... as curtisa mentioned it's more of a product of the mfg process for early fender.  

"hole needed for the notch in the nut"  If I'm not mistaken... you are referring to the notch that folks like graph tech put in their curved nuts... I think this is just meant for folks who want to use a rounded nut in a flat slot if I'm not mistaken.  I think the fender radius nut slots have no center slot/hole.  If I'm wrong here... would love to know.

graph tech nut

fender p bass nut

 

[Bizman62]

1 hour ago, mistermikev said:

the notch that folks like graph tech put in their curved nuts... I think this is just meant for folks who want to use a rounded nut in a flat slot

You may well be right there. If so, the contact area of such in a flat bottom slot would be much smaller than with a flat base nut. Which in turns would affect sustain not to mention that the material might give in under string pressure and start causing buzz and intonance issues. Most likely not as dramatic as the previous sentence sounds, though.

[mistermikev]

4 minutes ago, Bizman62 said:

You may well be right there. If so, the contact area of such in a flat bottom slot would be much smaller than with a flat base nut. Which in turns would affect sustain not to mention that the material might give in under string pressure and start causing buzz and intonance issues. Most likely not as dramatic as the previous sentence sounds, though.

yes... an air gap under the nut would seem like a bad idea to me.  that said... not sure anyone's picking that out of a lineup.  I think this nub is there because all sorts of folks just buy a nut w/o much thought to whether they need a radius bottom or not... and graph tech probably is combating returns in such an event that someone buys this to find out it's a flat bottom... also could just be due to an unknown radius and a need to easily match it.    sand down on the fretboard and then toss it in the slot.  I'll stick to flat bottom nuts for me lol.

[Bizman62]

1 hour ago, mistermikev said:

I'll stick to flat bottom nuts for me lol.

Following the K.I.S.S. philosophy, flat for me as well!

[mistermikev]

58 minutes ago, Bizman62 said:

Following the K.I.S.S. philosophy, flat for me as well!

tru dat

[AVClub]

Thanks guys! Essentially what I had thought, I will be sure on the first build to make it flat as I think there will be many other things I need to focus on in the build. It would however be fun to do some tests with different nut underside. geometries, although I predict there won't be much of a difference. 

@curtisa - Do you have any documentation on fender using bent laminations for fretboards? This is fascinating, what years was this popular? The particular guitar I am building this for currently has an "A" sized neck (Which is fun, but as a player its a good excuse to build a proper sized neck, plus the guitar already sounds great, and I can't wait with a bit more contact in the neck pocket to see if it sounds even better) and the rosewood board is quite thin (approx 1/8"), I wonder if this is a bent board? The guitar is a 70's musicmaster. 
 

[curtisa]

1 hour ago, AVClub said:

Do you have any documentation on fender using bent laminations for fretboards? This is fascinating, what years was this popular?

Googling 'Fender round laminated fretboard' turns up results. Early 60s to early 80s by the sound of it:

Slab Rosewood vs Laminate Rosewood | Page 3 | TalkBass.com

The History of the Fender Stratocaster: The 1960s | Fender Guitars

Some of the quotes in that first link suggest that the curved fret slots (and hence curved nut slot, I guess?) predates the round laminated fretboard introduced in the 60s, so maybe the curved nut was just an intrinsic byproduct of Fender's construction methods employed when slotting. A lot of what made Fender a leader in the early years was to heavily mechanise and automate the process of making guitars, much like a car assembly line.

[Bizman62]

2 hours ago, curtisa said:

A lot of what made Fender a leader in the early years was to heavily mechanise and automate the process of making guitars, much like a car assembly line.

Tangentially, that's behind the wood choices as well. They used what was available. The bodies are based on standard 2" (or5/4 as we're talking about hardwoods) thick planks, coarse sawn 2x8 is plenty good for a two-piece body. Similarly a 4/4 (1") or 5/4 (1 1/4") is thick enough for a neck without a headstock angle.

[henrim]

3 hours ago, curtisa said:

A lot of what made Fender a leader in the early years was to heavily mechanise and automate the process of making guitars, much like a car assembly line.

There is a lot to admire in the fabrication process inventions Fender made back in the day (maybe they still do). And there are not many industries that are able to sell products that were designed over a half century ago. Car assembly lines are not churning out 2CV's and Beetles anymore (although Beetle was manufactured long after it's best-before -date).