Kashuring Meat Utensils for Dairy Use
Question
Answer
It is customary to prohibit, and there are two reasons for this custom: either due to the concern that a utensil used within the day will be kashered, or due to the concern that one might use the same utensil for the opposite type without kashering.
However, it is permitted in several cases.
1. When kashering for Passover. (Mishna Berura, Siman 451, Se'if Katan 19)
2. If the utensil requires kashering because it was used for something prohibited. (Mishna Berura, Siman 509, Se'if Katan 25)
3. In a pressing situation (and when there is no other utensil, it is considered a pressing situation).
4. If 12 months have passed. (Responsa of Maharsham in the name of AA Botshash)
5. After the fact, if kashering was done, it is effective.
6. When selling utensils.
7. Some permit by first kashering for pareve, and then kashering again for the opposite type, but the opinion of our teacher, Rabbi Amram Fried, shlita, is to prohibit this.