you can shim the whole brass nut underneath with quality (thicc) printer paper, go slow, so you don't have to.
I just file a bit and then play it, once I'm close, I file less OR play it the next day and see if my opinion has changed on whether it's low enough...
It's fine to pay somebunny to do it, but they will just do it to a set specification, it may not be what your mood that day/week/month likes...
I have brass on a few basses and it's mostly because I have some brass stock laying around, not for "tonal" qualities...
I do one light stroke at a time. It takes forever, but I haven’t screwed up yet.
And Ahem.
I do this on all my basses related to the nut; I depress the 3rd fret and file each slot so that the string barely touches the 1st fret. I use a post-a-note leaf to test it - it should lightly grab when sliding it under the 1st fret. When filing - 2 rules; be patient and don't over-file. Better to keep going back & forth a little at a time until it's spot-on.
Thanks for all the great replies! I (finally) got the brass nut filed and my 7ender parts bass is playing nice! One more toy for the toy box.I've never measured the string height at the nut, but here is what I do anyway:
I file a bit, put the string back, press down between frets 2 & 3, tap the string against the first fret to check, and repeat as necessary. There should be just enough clearance for the string to make a tapping sound.
Make sure you are always filing at an angle, so where the string leaves the nut at the fingerboard is the high point of the slot.




