The Talmud relates the concept of “Cherev harei hu k’chalal” which indicates that a sword, or any such metal utensil, that touches a dead body adopts the status of that dead body vis-à-vis impurity. The implication would be that one who comes into contact with these utensils would then go through the seven-day process of purification from the beginning. The Rashash, however (Chagigah 23), asserts that this is actually not the case. Rather, any element that becomes impure through contact with such a utensil adopts the status of that utensil completely, to the extent that it joins the utensil at whatever stage it is in the process, and need only complete the process from that point on. The accuracy of this assertion was analyzed by R. David Rappoport (Mikdash David, 49) and the Steipler Gaon (Kehilot Ya’akov, Taharot, 53).