If you contact Empire they'll do it. What they do is have you buy a new axle, ship it out to Ken @ Zodiac Engineering and he does work. He does A LOT of them, I'm pretty sure a few people on here had him do theirs.
If you do it yourself, I'd imagine you'd need
-Hacksaw
-Tap & Drill set of corresponding sizes (3/8" tap & idk google for correct drill bit size)
-File & thread file
-Clamp/Vice of some sort
-Measuring device
-Cutting fluid
-Bolts, G-Sports will do.
With your locknuts on the axle, measure how much axle you'd need to cut by seeing how thick your dropouts are. make sure you cut the axle to where the remaining axle will sit in your dropouts okay, but also not stick out. You don't want them to stick out otherwise you won't be able to tighten it down.
File everything nice and smooth and use the thread file to clean the threads up. Next, secure it in the drill and use a bit of cutting fluid, start off with smaller sizes so you don't jam it. work your way up to the size it needs drilled while using cutting fluid to make it easier. Be sure to ease in and out so metal shavings don't jam it either. Idk if you should drill the whole way through or not, maybe. But drill it on both sides at least enough for the bolt to thread in fully.
Next, with it still secured in the drill, start tapping it. Remember to ease in and out, and use cutting fluid. maybe damn sure it goes in straight, otherwise you'll fuck the whole thing up. Again, do this to the bolt's lengths at least. Once you're done, use an air compressor if you have access to one and blow all the metal shavings out of it. If not, just blow into it or something to get all that shit out of there.
Once you have it all cleaned out, grease the bolt threads up and thread it in a few times on both sides just to make sure everything works okay before mounting it. If everything does, go ahead and put your hub back together and ride it! if not, well then you fucked up haha.
I've never actually done it myself, but that's how I would guess it is. It seems like that anyway, hopefully this helps.