Thoughts on heavy gauge strings in this nut

You're nut slots need to be wider not necessarily deeper, unless the depth was wrong to begin with. Guaged nut files are best, you can use all kinds of stuff but you're more likely to mess it up.
Also a good idea if the depth is already situated you can throw some pencil marks in the bottom of the slot to let ya know if you're hitting the wrong spot.

Last, putting a string in a nut slot cut too narrow for it is a realy easy way to break it.

 

You're gonna spend 60-70 dollars for three files you'll use for 5 minutes and then have no further use for? Get yourself a decent set of handyman drill bits, a vernier caliper with a digital readout and a small packet of sand paper for 30 dollars. Find the appropriate size drill and wrap a piece of sand paper around the bit and do the filing that way. Once done, you will have saved 40 dollars and will have some tools that will actually be of some use to you.

 

I think it's gonna depend on whether @spantini ever plans on doing this again. I'd say if ya like to tinker and will have more basses in the future they're a great investment.

I bought a set of the two sided ones from stewmac when I was 18 and im now 35 and they've served me well hundreds of times.
I can't vouch for those Hosco ones but they look right? Kinda hard to say as some files have cheap steal and some do not.

 

Also fwiw I believe there is a welder's tool that is gauged and can work on the cheap but the name escapes me.

 

BINGO!

 

Just remember, it’s not about where the topside of the string is in relation to the nut, it’s all about where the underside of the string is in relation to the top of the first fret.

 

That doesn’t mean the nut slots are too high - it mat just be a function of the heavier strings. What’s the gap at the first fret now?

 

Press the string down between the second and third fret and look for a gap between the string and the first fret. It should be about the thickness of a hair. But be sure you have set the witness point at the nut first or you will get a false reading.

 

This does inside, outside, and depth in inches or mm; all metal case and controls, no plastic. Less than $20. They were so reasonably priced I bought a manual one as a back up.
Stainless Steel Digital Caliper Vernier Micrometer Electronic Ruler Gauge Meter 722699281491 | eBay

 

The only caution I have about this concerns the automatic on feature. When you pick it up if you don't turn it on, it will turn on when you open the caliper jaw. It will also turn on if the jaw moves the slightest amount while stored. To insure you don't kill the battery, you need to use the locking screw when storing it.

 

That is far too much. As I said it should be like the thickness of a hair ( an exaggeration) - but about as close as you can get without it actually touching.