How do you radius the bottom of a NUT?

[davidos]

I don't have radius blocks and it's a nut for a 9.5 radius fingerboard... Any tips appreciated!

 

[Mike9]

The easiest thing to do is get a curved nut - Tusq has a center tab that you can cut off and file smooth. Guitarparts Recourse.com has curved bottom bone nuts. Otherwise it's cut and try. If you have access to a band saw you can make a convex radius block -

 

[fr8_trane]

If its an oversized nut blank put it in the slot and use a pencil sawn in half to scribe a radius line then sand using the line as a reference.

Courtesy of Rob Distefano @ Frettech:
if the fretboard nut slot is curved, drawing the radius on the nut blank allows you to sand in the proper board radius onto the nut bottom so that it will seat properly inside the nut slot, and contact all of the wood with no gaps or flat spots, B) whether the fretboard nut slot bottom is curved or flat, once the nut blank is seated in the fretboard nut slot, use the half pencil to scribe a line on the nut blank - this line indicates two things: 1) you'll grind down the excess nut blank top to within about 3/32" of that line, and 2) you never wanna cut a string slot below that line!

Here's the full tutorial
http://www.frettech.com/

go to info--> nut making tutorial

 

[Jack Briggs]

I never refit curved bottom nuts. I file the slot flat and fit a flat bottomed nut, then nobody has to face this hereafter on the guitar.


Cheers,

 

[fr8_trane]

I never refit curved bottom nuts. I file the slot flat and fit a flat bottomed nut, then nobody has to face this hereafter on the guitar.


Cheers,

I like that. Easier is better.

I don't really get why they curve the nut slot in the first place. Is this some holdover from the vintage correct committee.

 

[Jack Briggs]

I like that. Easier is better.

I don't really get why they curve the nut slot in the first place. Is this some holdover from the vintage correct committee.

The slot is curved because the entire fretboard - nut slot included - is slotted on a gang saw with the 1/8" blade cutting the nut slot. Since the board is held in a pendulum jig, all fret slots and the nut slot are cut to the radius needed for the fingerboard, mirroring its radius.



Cheers,

 

[fr8_trane]

That makes sense.

So the guitars with flat nut slots are the exception?

 

[John Thigpen]

It's time consuming but not difficult. Use some sticky-back sandpaper (I use 180 and 320 grit) and attach it to the fretboard. Rub the bottom of the nut against the sandpaper until you achieve the correct radius.

John

 

[Soapbarstrat]

The radius of the nut slot bottom is not always the same as the fret-board surface radius.
Off-hand from memory, I know I've worked on recently made Fenders that had a 7" radius board, but the nut bottom was something more like an 11" radius. Fret-slots cut at a much flatter radius than 7" too, so I think their "gang-saw" is probably swinging on something around an 11" radius.
Anyway if you make a new nut and don't match the radius on the bottom, there's a good chance the nut will crack apart when you press it down in the slot.
I used to go the whole 9 yards with checking the radius of the slot, then machining a perfect matching radius in the new nut bottom, but never got paid enough for all the trouble.

 

[walterw]

I never refit curved bottom nuts. I file the slot flat and fit a flat bottomed nut, then nobody has to face this hereafter on the guitar.


Cheers,

careful though, i know plenty of vintage fender fetishists who would completely freak if i did that to their guitar.

plus, i've seen a few bullet-truss rod fenders where the bullet was already breaching the saddle slot a little, so flattening it would be a bit of a trick. (although now that i type this, it occurs to me you could just back the nut all the way off, then flatten the slot. it would still mean a big gap in the middle of the bottom of the nut, and it would still freak out a lot of owners.)

i don't have a "cool" method for radiusing the bottom of nuts, so i just use my radius gauges to get as close as i can to the nut slot radius (in case it isn't exactly the same as the fretboard) and trace a line off the right radius gauge. i then rough the nut bottom in on the round end of the belt sander.

now if the fretboard radius matches what i'm looking for, i lay a strip of sandpaper on the fretboard, and rub the nut on that to get my smooth curve.

 

[bunny]

First I roughly shape the bottom of the nut blank on a sanding drum (good to have a right angle base). Then, if the guitar is a Fender, I may stick a strip of sandpaper near the nut slot. Of course this is a quicky and presumed the fretboard radius is ok. A good nut is hard to find))

 

[John Thigpen]

The radius of the nut slot bottom is not always the same as the fret-board surface radius.
Off-hand from memory, I know I've worked on recently made Fenders that had a 7" radius board, but the nut bottom was something more like an 11" radius. Fret-slots cut at a much flatter radius than 7" too, so I think their "gang-saw" is probably swinging on something around an 11" radius.
Anyway if you make a new nut and don't match the radius on the bottom, there's a good chance the nut will crack apart when you press it down in the slot.
I used to go the whole 9 yards with checking the radius of the slot, then machining a perfect matching radius in the new nut bottom, but never got paid enough for all the trouble.

Obviously, I haven't found the nut slot radius to be different from the fretboard, as I have never had this problem on the half dozen or so that I have done. I did pick up some Stew Mac radius guides recently and can check this in the future. These are all my personal guitars, so I can put in as much time as my patience will permit (sometimes not very much) in order to get it correct.

John

 

[levelfrets]

It's time consuming but not difficult. Use some sticky-back sandpaper (I use 180 and 320 grit) and attach it to the fretboard. Rub the bottom of the nut against the sandpaper until you achieve the correct radius.

John

Thats what I do too. Works everytime.

 

[davidos]

Is it possible that this nut has a 7.25" radius while the fretboard is a 9.5" radius?

 

[walterw]

Is it possible that this nut has a 7.25" radius while the fretboard is a 9.5" radius?

that looks like 7.25" to me! let me guess, is this from an AVR hot rod? maybe they take necks already pre-cut to 7.25" (nut and all) and flatten the fretboards to 9.5"?

 

[Boris Bubbanov]

Look at that!

It appears there's an impression left of the fretboard wood that is flatter than the underside of the nut itself.

My eye tells me it is possible that this nut, in this application, allowed more space under the D and G strings than it did on the outboard strings. That it never was a proper fit.

How does Fender fabricate their factory installed nuts, anyway?

Making me think that "cyclovar" or whatever they use is:

1) Highly resistant to creep under pressure from the strings; and/or

2) The glue worked real fast and just froze things in place.

I find a graphtech or tusq nut will creep under string pressure and eventually conform to whatever radius it is applied to. Within limits, obviously. I use Titebond which doesn't reach full strength before the nut has a chance to get bedded in.

 

[Soapbarstrat]

Look at that!



How does Fender fabricate their factory installed nuts, anyway?

Well, the bottom radius is quite perfect, because the blank was molded with the radius in it. But, as you can see by that photo, that the factory worker's nut slotting skills are nothing to write home about. Ok, maybe someone outside the factory messed with those slots, but I've seen them out of the factory that are just as screwed up. I worked on one not long ago, where the factory worker made the A slot too low, which looks like is going on in that posted photo as well. Heck, if you're going to slot em poorly, at least leave em too high, so someone can tweak it right.

 

[Structo]

When I started making my own bone nuts the first couple of necks had flat slots.
Then came along a strat with a curved slot.
I did it just like the guy that posted earlier by scribing a line from the fret board to the nut.
I didn't check to see if the slot was the same radius as the neck surface.

I suppose you could get one of those tools that conform to a shape the trace from that.

I don't have a regular drum sander but I have a Dremel tool with the drum sander attachments.

The Dremel is an essential tool IMO for making a nut.
With the drum sander, it just takes minutes to get the nut into a rough shape.
Then I use fine files to angle the back side.
Nut slot files are also necessary for slotting the nut.

Then I use different grades of sandpaper to smooth the nut, then buffing it with rubbing compound and finally polishing it with polish.

Don't waste your money on the files made from feeler gauges as sold on ebay.
They aren't sharp enough to cut bone and it will take forever.

I bought the nut files from Warmoth, they are the best deal I have found for them.

Very satisfying to make your own nut and have it perform great!

 

[davidos]

What is the Demel Drum Sander attachment? I have a Dremel and need to get on of those!
Thanks for all the replies!

 

[kellyweeks55]

How do I cut a pencil in half? I know that sounds like a dumb question but I can't just throw it on the table saw.