The only time that I have seen this is when the slot has been made after the board has been radiused, thus following the radius of the top. In my opinion, it makes more sense to make the slot flat-bottomed, making the nut easier to work with.

These are just my thoughts, and I may be wrong in my line of logic.

Hi Jon, Thanks for your feedback on this — I completely agree with you! Nuts are critical components and making them conform to a curved bottom surface is only making things more complicated than necessary, in my opinion, at least. Cheers!

Fender follows the radius of the fingerboard faithfully

Hi Chip, very interesting. I thought that was the case with Fender but was never completely certain. I make Fender-style necks but don’t radius the nut slot. And, I don’t have the tooling for it as well.

if you slot your FB with a table saw or with a fretsaw by hand you need the flat style. if you are using some type of roller jig to slot it after the radius is done as most big companies do you need the radius bottom nut

Hi Mark – That is very interesting. I use a fretsaw, by hand, so flat-bottomed nuts/nut slots is what I do. Good to know I’m doing this correctly. As for the more industrial approach, it would be interesting to see how a 1/8-inch nut slot bottom is actually radiused! That is intriguing to me. Many thanks!