A Shechitah Knife from an Executioner’s Sword
I just came across this interesting responsum from Sefer She’eilat Ḥacham Kanah Avraham from Abraham ben Daniel of Aptashni (18th c. Poland). (here)
Question: A ritual slaughterer bought a sword from an executioner who had used it to execute people, and he gave it to a blacksmith to make it into a knife for ritual slaughter, is it permitted to use it to slaughter or not?
Answer: It is forbidden to slaughter with a knife like this since we hold that a sword is like a corpse and it transmits impurity to meat that is slaughtered with it. Although it is permitted to slaughter with it since a knife is purified through immersion.
It seems as if the solution was to immerse the knife in either a ritual bath or a body of water that was fit for immersion, and then it would be permitted to use.