2,470. Kashering a Knife

Maachalos Assuros 17:7

If someone buys a knife from a non-Jew, he must either purge it in fire until it’s white hot or sharpen it in a grinder. If the knife was perfectly smooth without any imperfections, it may be thrust into the hard ground ten times, after which one may use it for cold foods. If the knife has imperfections, or if it’s perfectly smooth but he wants to use it for hot foods or to slaughter with, he must purge it in fire until it’s white hot or sharpen it completely. If one performed slaughter with such a knife before kashering it, he must scrub the place where he slaughtered the animal. If he peeled off a layer of the flesh from there, it’s even better.

Maachalos Assuros 17:8

If a knife was used to slaughter a treifa, one may not use it to slaughter another animal until it’s been scrubbed – even with cold water – or wiped off with worn rags.