Every time I make a 12 string, the cutting of the nut gets the better of me. But on this one, it just "clicked" so I thought I'd share. (Also so next time I can go back to the archives and figure out how I did it.
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Start first by marking the outer points of the nut.
Next mark the two outer strings, their set-in from the edge of the neck. In this case I went 1/8 on the bass side and 3/32 on the treble side.
Now that we have the limits we're ready to lay the string spacing in. One thing to remember during this, and this is why 12 string nuts are so confusing, is that the two marks we have represent one main course string and one sympathetic string.
So at this point you need to determine the spacing you want between the main course and sympathetic string. I've chosen 3/32 on the bass side and 1/16 on the treble side. Transfer those marks to the nut. Remember that both measurements need to move toward the center of the nut.
Now with the trusty string spacing tool from Stew Mac (this should already be in everyone's tool box) you'll want to connect the main course marks and the sympathetic course marks. So in this case, the sympathetic course are the strings more toward the bass side of the neck. So I'll connect them with the spacing tool.
Move the tool over and do the same for the main course strings. For me, I had to use different "slots" of the tool because my distances between strings changed from E to e. What this does is give me a gradual change across the neck.
Here's what the final layout looks like.
Hope this was informative. Let me know if I was unclear about anything.
