Yes for some things Kosher is too coarse for. But I will sometimes set my grinder to fine and use sea salt in his things that call for table salt and it works well but it's a lot of grinding to make a teaspoon or more.
I do grind my own chuck sometimes.
I have a meat grinder for my stand mixer.
I guess they would use iodine salt commercially, but it never says that specifically. Because it has been used most commonly maybe we are safe in assuming it is.
