Official Luthiers Forum!

See what I posted above about using a .013" gauged nut file and your thumb as a fence to start the cut. I make a lot of nuts and do this for a living and it works for me and my clients. Remember we are only starting the slot we can once it's started walk the slot over to where it needs to be with frequent remeasuring. We will also be removing the nut material that we just scribed as we take the top of the nut down toward the end of the process.

So think of the marking more as getting started in the right spots without the need to be perfect but perfecting the spacing as we file down. It's a process and we have opportunity to refine.

Here's a pic from a tutorial I did here 15 years ago of how we take top nut material down after roughing in the nut slots. It's done on the actual instrument sacrificing the strings, the crappy set it came in with that will be tossed anyway. We file right to the strings but I want to illustrate how important it is to not use commercial nuts and instead make them for each instrument. The actual radius of the fret plane and the strings will be telegraphed to the top of the nut when I am done.

There is a lot to making a good nut and a good, bone nut can last a 100 years or more and look great the entire time. Wish I could say that...

Yes, I do this as well,but I just rub my dirty finger in it to see the grooves.....

I recently went through the exercise of determining string spacing for a 10 string mandolin. Had to build my own bridge, no one sells them for 10 string. As you can see from picture, I tried several spacings at the nut. The final is at the top. Print to full size, then cut and stick it to nut. Worked great. This was done with sketchup. There is advice on the web for course spacings. The rest is up to you and is based on nut width and typical offsets from both outside edges.