I've done this a few time, but I have a chunk of bone nut laying around that I will file to create some dust instead of baking soda.
it works as an emergency fix but i mostly hate it; the resulting amalgam tends to be soft and grabby, especially on guitar strings. (when i do use it i'm scraping a bone blank to make the dust like @Hopkins does.) if i'm not gonna remove the nut to shim or replace, what i've found to work much better is to chisel, carve or saw off one tiny little solid piece of the nut material i need and essentially inlay it into the slot. i'll even file the slot bigger or more square to fit the piece better, supergluing it in once i've got the fit. done right, after filing the slot back down to where it should be the result is the string rides on solid nut material instead of a glue/dust mixture, so the tuning and wear performance is not compromised.
Resurrecting a slightly old thread. I have a nut where three of four slots are just *slightly* too deep (fretting at the 3rd fret and there is no gap under the 1st fret). Instead of cutting a new nut, would it be acceptable to shim the bottom of the entire nut with some copper shielding material? I think that would give me enough clearance between the strings and the 1st fret, and I could file the one slot that is too high. If it matters---it's a flat-bottomed nut.
A shim could be used as a permanent fix and would be preferable to filling the slots. It would be best though, to use a shim material similar to the nut. For example, I had an upright bass ebony nut that was too low and glued ebony veneer to the bottom. Also it should be a material that will bond well to the nut bottom. The color can be important if the nut bottom is exposed all the way around like a ramp nut that sits against the end of the fretboard. Color not so important if the nut sits in a slot with only the narrow ends of the shim exposed. -
Good tip. I may use wood veneer as the shim material, to match the neck material. Since only the ends are exposed, the color match won't be critical.
I have actually found, when using bone nut dust instead of baking soda or baking powder, that the resulting repair can actually be harder. Even with a plastic nut, I repaired one guitar over twenty years ago like this, and when I was done, not only did the open high E string have more sustain, but the repair has lasted all these years, and will probably last that many more!
Here are some related products that TB members are talking about. Clicking on a product will take you to TB’s partner, Primary, where you can find links to TB discussions about these products. Browser not compatible