Making my first Mandolin nut

Q: I have the dreaded first fret buzz on one of my "D" strings and so I've decided to take on the project of replacing the nut with one of my own making. (Just had a local luthier do it and the job didn't last long at all.)

I bought the nut making kit from Stewart MacDonald complete with files. But now I'm wondering if the files might not be too big for the Mandolin since the kit is basically for the guitar. I can find strings which come as close as .001 - .003 of an inch to the smaller file sizes. Would those tolerances be too loose for my mandolin nut?
Thank you, Jim.

A: Making the nut slot slightly bigger is fine. Don't go slightly smaller. With slightly bigger, the bottom of the slot is round and holds the string in place. If the slot is too narrow it will pinch the string. When you tighten a tuner it will increase the tension on the string between the nut and the string post, and break the string. Any time a string breaks between the string post and the nut it means that your nut is too tight.

If your choice is sloppy big or slightly small, use the small file and rock it in the slot. Test the string in the slot. If it grips, make it slightly bigger until it slips smoothly.

I find that the Stew-Mac nut files are not very accurately marked. I measure mine with a micrometer and remark them as necessary. Stew-Mac has a great return policy. If mandolin is all you do, trade the guitar files in on mando files. Or, just buy a set of mando files and be ready for anything.

Steve Mason