If you want a really fine grind in a hurry you can use one and get ok results. You have to let it rest every 30s or so to cool down or it heats the grounds too much. I liked to shake it while grinding too. It isn't quite Turkish grind and there are a few large pieces that won't get full extraction, but if you want really fast extraction (or fast intentional over extraction) it works.
And salt is a lot harder than a coffee bean. Blade is probably a really weak/soft metal. Might be harder than salt on the Mohs scale, but that just buys you time.
Blade also gets kicked around more going around the salt instead of grinding through, more bending = shorter lifespan.
