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.

December 9th, 2011 at 2:46 am
I don’t understand why a knife that is טמא cannot be used for שחיטה because it will מטמא the meat, there is no איסור to eat meat that is טמא. The only similar idea is found in הלכות ארץ ישראל by אלדד הדני who writes that a person who is טמא cannot do שחיטה, but as we all know he was a charlatan.
December 10th, 2011 at 2:56 pm
This is extremely strange: why would immersion in a miqve do anything to help purify a knife which had become tamé through corpse-contamination? According to normative halakha, nothing purifies corpse-contamination except for the ashes of the Red Heiffer. (And I’m not sure whether even that works for the חרב הרי הוא כחלל, maybe only for the people who have come into contact with it or with a corpse.)
December 10th, 2011 at 3:01 pm
With all due respect, Mr. Gavriel I believe that you have forgotten an explicit passage in Nachmanides (Ramban to Numbers 19:16) who writes that חרב הרי הוא כחלל does not require purification through the ashes of the Red Heifer. By the way, did you receive my regards through Eliezer Braun?
December 27th, 2011 at 6:22 pm
Reb Chaim HaQoton: Ramban says that one who comes into contact with the חרב does not need הזאה, not that the חרב itself does not: