You wrote in Insights to the Daf-
>>[II] APPLYING A "ROV" TO TIME
QUESTION: The RASHASH asks a basic question about the Safek whether the wife was Mezaneh before or after the Eirusin ("Tachtav or Eino Tachtav"). Why don't we simply follow the principle of "Rov" and assume that the Be'ilah occurred during the longer of the two time-periods! That is to say, if she was unmarried for most of her life, we should assume that the Be'ilah occurred during the time period when she was unmarried!
ANSWER: We cannot apply a "Rov" to time. There is a general principle in the laws of "Rov" that when the subject of the doubt involved is "Kavu'a" -- that is, where the Safek arises about the status of an object that is immobile and established in its place -- "Rov" does not apply. Therefore, when it comes to a question of which day an act occurred on, we cannot apply "Rov" to days and say that certain days are in the majority and thus the act happened on those days. (In other words, Rov can only determine what person or object did an act, not to whom the act was done or when it was done.) <<
My question is-
How do you accomodate the law in OH 451:6 that kelim are considered
hametzdig or not according to rov tashmishan, that is according to their relative frequency of use one way or another, that is rov in time?
First,let us clarify the Halachah which you mentioned. The Halachah is not do determine whether or not a Keli is Chametzdik, rather how to Kasher a Chametzdik Keli. A Keli which is only used for cold may be just washed, for cooking needs Hagalah etc.
The Rov we were refering to, is a Rov through which we are trying to determine the nature of a specific act or a specific object. For example, if we wish to know whether a specific piece of meat is Kosher or Neveilah, we can deduce this through Rov. On such a Rov there is a limitation that it cannot be used to clarify the Safek if it is "Kavu'a."
The Rov which you mentioned is not used to clarify anything. We know that this Keli was used both for cold and hot. Our only question is what type of Hechsher does it need, and for that we follow the Rov. We say that if it was generally used for hot then it needs Hagalah etc.
The question arises, why do we follow the Rov in that case. The principle of Hechsher is "k'Bol'o Kach Polto," i.e. a Keli secretes what was absorbed in it only in the way in which it absorbed it. Therefore, even if one only cooked in a pot once, and one hundred times it was used for cold, one should still need Hagalah to secrete what it had absorbed that one time.
The answer to this is that mid'Oraisa we don't need Hechsher at all, for what is absorbed is "Pagum," unfit for consumption. The Chachamim who required Hechsher said that it suffices to Kasher it in the way it is generally used.
Dov Zupnik