Those of you learning the daf might be interested in taking a peek at the Ramban at the end of Yisro (the daf yomi learners I mentioned it to loved it). Rishonim offer various reasons why the Torah prohibits using an iron chisel to square away the stones of the mizbeyach. Ibn Ezra says that the leftover shards might be tossed in the garbage or used improperly or even worshiped. Rambam sees the whole prohibition as a safeguard against even maskis type avodah zarah. Ramban expands on the Midrashic idea that iron, which is used in weaponry, serves to shorten man's life, and therefore stands in contradiction to the whole purpose of service in the Mishkan, which is to extend and enrich life. Even the sockets of the Mishkan boards, which had to be made of metal, were not made of iron. How then were iron knives permissible to be used for slaughtering animals? Ramban cleverly answers that this proves the point the gemara in Zevachim makes a number of times: shechita is not considered avodah.
The Meshech Chochma and others (see footnotes to the Chavel ed.) point out that there seems to be an exception to the rule that the Ramban does not account for. When the Chashmonaim rededicated the Temple they did not have enough gold for a new menorah and therefore had to make a temporary one out of iron. Even if the lighting of the menorah can be done by a zar and is perhaps not technically avodah), the hatavas haneiros must be done by a kohein. The Chavel edition quotes an answer from R' Meir Arik: the menorah oil was first placed in a kli shareis before use; the menorah itself was not mekadeish anything. I'm not sure I understand this answer -- if the Ramban extends his principle to cover even the sockets used to hold the boards of the Mishkan in place, why would it not apply to the menorah, even if it does not serve as a mekadesh?