Proportionately Cutting a Guitar Nut, Cheap and Naive

I ordered a 1/4" blank bone nut from StewMac and decided to make my own.  I'd never done that before.  I cut it to length with a hacksaw and to shape with 100 grit laid on 1/4" plate glass.  I've read that 3/16" of bearing area is sufficient.

I cut it roughly to height with the hacksaw as well.  Since I knew that the original nut was a bit high, I used the one to draw a line on the other, placed the new nut in the jaws of the vise with just the discard area sticking up, and chopped it flush.

I used a tiny hobby triangle file to start the slots for strings 1 and 6.  Then I was faced with the problem of spacing the rest of the strings.  This was fun.  I wanted to space the strings proportionately, which means that instead of being spaced evenly on center, they will be spaced evenly based on the distance between their edges.  First, I needed a jig:

I obviously made that, and it was obviously cheap.  I put six nuts on a small threaded rod and used them to enforce my desired string spacing.  This works best, I think, on a traditional 3+3 setup lacking straight string pull. - the horizontal break angles pull the string into the adjustment nuts.

Then I calculated thusly:

1. 1 and 29/64" between the high and the low strings =  1.453125
2. The total diameter of strings 2 through 4 = 0.114
3. The total space to be divided among the remaining five string gaps = 1.339125
4. The amount of space between each string = 0.267825
5. Multiplied by 64 to make it 64ths = 17.1408

I thus attempted to put 17/64" between every string - that means diameter to diameter or what have you.  That way thicker strings get their share and fingers get the same amount of space around each string.  Is the better?  Who can tell?  Measuring was hard with my eyes.  Around a year ago I noticed that I have trouble at close range with tiny little 64ths of an inch.  Luckily, I found this weird lens in the junk drawer of my tool chest:

It's badly scratched but it actually worked well for this task.  Once I had the spacing, and believe me that (for me at least) committing to a measurement is a real act of faith, I marked each side of each string with a pencil.  Not an ordinary pencil, but a pencil sharpened on a flat sheet of sandpaper to make a knife edge.  

Then, as I said, I started each slot with a hobby file of small size and triangular cross section.  This is nerve wracking in itself:  I couldn't commit a deep cut until I was sure the groove had landed exactly between the two bracket lines.  When I'd cut deep enough to just touch both lines, and that contact occurred at the same time, I had confirmation that I'd hit the center properly.

Then I finished the slotting with a cheap set of welder's torch tip cleaners, a trick I'd found in several places on the internet.  I am unable to make the exact citation, and I do not know who originally proposed this solution.

They look like that.  I just picked the one that looked next-size-up from my string using my untrusty eyeballs and my fingers (important).  The large ones were able to hold up to the filing pressure, while the small ones need to be supported by your fingers wherever you can hold them.  I settled on one finger from my free hand on the edge of the nut, and one free finger from my filing hand pushing down on the file right where it crossed the nut.  It worked.

My next task will be more outlandish:  straight pull conversion.