Gemara

Question: Why does Tum'ah of the Shulchan depend on being moved? It is covered with gold!

(Mishnah): If a table was covered with stone (which is not Mekabel Tum'ah), it is Tamei only if there remains an intact place (not covered by stone) to hold cups;

R. Yehudah says, it is Tamei if there remains a place to hold pieces (of bread or meat. This shows that the Kli has the law of the covering. Metal Kelim, even stationary, are Tamei!)

97a - Answer: The Shulchan is an exception, for the Torah calls it a Keli Etz - "Ha'Mizbe'ach Etz... Zeh ha'Shulchan."

Shabbos 15b (Reish Lakish): Chachamim decreed Tum'ah on glass Kelim. Since they are made from sand, Chachamim made them like Klei Cheres.

Question: Tevilah in a Mikveh is Metaher them (unlike Klei Cheres)!

(Mishnah): Pitch or Mor (a spice or sap) on glass Kelim is a Chatzitzah (blockage) that invalidates Tevilah.

Answer: Tevilah is not Metaher pure glass. The Mishnah discusses Kelim that were punctured and sealed with a drop of molten lead. It is like R. Meir, who says that the law depends on the Ma'amid (what maintains it. Tevilah is Metaher metal Kelim);

(Beraisa - R. Shimon ben Gamliel): If a glass Kli was punctured and sealed with a drop of molten lead, R. Meir is Metamei, and Chachamim are Metaher.

59b (Mishnah): A woman may not go out (in Reshus ha'Rabim on Shabbos) with a ring without a stamp. (If she did, she is exempt.)

Inference: If she went out with a ring with a stamp, she would be liable. This shows that a ring with a stamp is not an ornament.

Contradiction (Mishnah #1): Ornaments of women are Teme'im, e.g. rings with or without a stamp...

Answer (R. Zeira): Our Mishnah is like R. Nechemyah (who says that the primary part of a ring is the stamp. Women do not normally stamp, so it is not an ornament for them);

(Beraisa): If a metal ring has a wooden stamp, it is Mekabel Tum'ah (like a metal Kli). If a wooden ring has a metal stamp, it is Tahor (like a wooden Kli that does not hold anything);

R. Nechemyah is Metamei.

He judges a ring according to its stamp, and a yoke according to its pegs...

Chachamim judge (all of these) according to the Ma'amid.

Rishonim

Rambam (Hilchos Kelim 4:4): If a Keli of wood or bone can hold something and it was plated with metal it is Tahor, since the plating is Mevatel them. The plating itself is Tahor.

Rebuttal (Ra'avad): What is the source for this?! Just the contrary, if a Keli cannot hold anything and it was plated with metal, this causes that it is Mekabel Tum'ah! We sometimes find that the Keli is Batel to the plating.

Rosh (Avodah Zarah 5:35): Some obligate Tevilah for Kelim with of iron braces, e.g. a reinforced bucket, for the law depends on the Ma'amid. I disagree. Who says that the Halachah follows Chachamim, who follow the Ma'amid? Perhaps the Halachah follows R. Nechemyah, who does not follow the Ma'amid! The Gemara established the Stam Mishnah like him. Also, even if we follow the Ma'amid, it does not need Tevilah, for one does not use the place of the iron. It is unlike the Klei Seudah (food vessels) of Midyan. This is why one need not immerse a Kli Cheres covered with lead on the outside.

Mordechai (Avodah Zarah 859): The Ri says that if one gave a Kli to a Nochri to fix it, even according to the opinion that a craftsman acquires improvements to a Kli, he need not immerse it. It is not called the Nochri's, therefore, it is unlike Klei Midyan. However, if it was punctured and held less than a Revi'is, and the Nochri put metal (to seal it), it must be immersed. We hold like R. Nechemyah, who says that the law depends on the Ma'amid. (Our text says oppositely.) If he sewed it with a metal thread, this is nothing. It merely joins the pieces. If one bought from a Nochri a bucket with iron braces, he need not immerse it. Even though the law depends on the Ma'amid, this is when he uses it through the Ma'amid, e.g. a hole that was sealed. Here, the Ma'amid is not in the bucket, so it need not be immersed. Rabbeinu Meir obligates Tevilah. We say that Chachamim made glass Kelim like Cheres because they are made from sand. If they were punctured and sealed with a drop of molten lead (one can immerse them, for) we equate Tevilah to Tum'ah, and it depends on the Ma'amid. A Teshuvah of Rashi says that one with Yir'as Shamayim will immerse them with a new Kli, which definitely needs a Berachah, and exempt these.

Mordechai (ibid.): Rabbeinu Meir says that if a pan was punctured, and fixed, if the hole was on the bottom and was big enough to be Metaher it, i.e. liquid enters through it (like the law of a Kli that holds liquids), it ceased to be a Kli. When a Nochri fixes it, this is like a new entity, and he must immerse it. If so, the same applies to a hole in the side, for above the hole it is as if it is not a Kli, since it cannot hold liquid. If a metal Kli held a Se'ah, and one added to its height and now it holds two Sa'im, one must immerse it again due to the addition, since the law depends on the Ma'amid. It is as if the entire Kli above the hole is new. If a flask was made of Tahor and Tamei (metal), a Tosefta says that it depends on the bottom, which holds (liquid). It is Tamei only if the bottom was from Tamei metal. Rabbeinu Shmuel of Bonvira said that if wooden cups have metal around the brim or stand on a metal leg, one need not immerse them, since the wood holds the liquid. However, if they are covered with lead inside, Mishnayos prove that they are like metal Kelim, and one must Kasher them and immerse them.

Poskim

Shulchan Aruch (YD 120:6): If a wooden Kli has iron braces outside that are Ma'amid it, one need not immerse it.

Beis Yosef (DH uv'Inyan): The Mordechai brings Tosfos, who exempts. He then brings Maharam me'Rotenburg, who obligates, because Tevilah depends on the Ma'amid, just like Tum'ah does. We discuss a Kli made of boards, and a wooden bottom. They are held in place through pieces of iron on bottom, near the top and in the middle.

Darchei Moshe (5 DH uv'Agur): The Agur holds like the Tur (who exempts). Isur v'Heter ha'Aruch says to immerse it without a Berachah.

Taz (8): The Tur says that even though the law depends on the Ma'amid, i.e. like R. Meir, this is when one seals a hole with lead. The lead is Ma'amid the Kli, i.e. enables using it. It is as if the entire Kli is of lead. However, here the Kli is not used on the side (i.e. the outside) where the Ma'amid is.

Shach (12): The Shulchan Aruch is difficult. The Beis Yosef (below) ruled that one should immerse it without a Berachah, for it is a Safek whether the law depends on the Ma'amid. Also Maharil and Isur v'Heter say so.

Gra (16): Even Chachamim who follow the Ma'amid do not require Tevilah here, for one does not use the metal. Only Klei Seudah must be immersed. Plated Klei Cheres must be immersed, even though they are Tehorim. Tevilah depends on the plating, for the plating is inside and it is the part that is used (touches the food).

Shulchan Aruch (7): A silver cup connected through a wooden Kli must be immersed.

Beis Yosef (DH Kasav): Semak says that a silver cup connected through a wooden Kli around it must be immersed, since one uses the silver. This is like a wooden Kli with iron supports (Sa'if 6). The Tur explains that one must immerse it because one uses the silver, 'but outside, not', i.e. he does not use the wood outside. Alternatively, first he teaches that a silver cup connected through wood around it must be immersed because one uses the silver, like we said about a wooden Kli supported by iron braces (it depends on what is used). Then he says 'but outside, not', i.e. if the silver is outside, even though it is Ma'amid the wood, one need not immerse it, like the wood box with iron braces, for it depends on the part used for liquid. One must immerse it only if metal is used for the liquid. We are not concerned for the Ma'amid at all. This explanation is primary.

Beis Yosef (DH u'Mah): The Tur says that some are stringent to immerse it without a Berachah. It seems that this refers to both, i.e. a silver cup with a Ma'amid of wood, and vice-versa. They are unsure whether we hold like R. Meir, who follow the Ma'amid, or like Tosfos and the Rosh, who say that we do not follow the Ma'amid. Therefore, one immerses it without a Berachah. We hold like this.

Taz (9): If the Tur explains like this, he should have been in doubt also about the barrel with iron braces! The Beis Yosef equates them! His ruling here contradicts the previous Sa'if, in which he exempts even according to the opinion that follows the Ma'amid! Rather, the Tur explains that Semak discusses one Kli inside another. Semak says so explicitly! A little of the outer Kli is seen inside. Therefore, it is a Ma'amid, like R. Meir discussed. Some are stringent to immerse it without a Berachah when the outside is silver. When the inside is silver, surely one immerses it with a Berachah. The Ma'amid cannot be Mevatel the primary Kli. The Shulchan Aruch retracted from what he wrote in the Beis Yosef. He requires immersing it, i.e. properly, with a Berachah. The stringent opinion discusses only when the silver is outside, like I explained. The Bach explains like this, unlike the Levush, who says that the Shulchan Aruch means without a Berachah. The latter opinion in the Tur holds that one blesses even when the outside is silver, for the law depends on the Ma'amid. This is clear from the Rema in Sa'if 10. However, I rule that we immerse it without a Berachah here and there.

Shach (13): The Shulchan Aruch connotes that one immerses it with a Berachah. The Beis Yosef not to bless. That is when the cup is unusable without the wood. Here, it is a proper cup, just it is connected to wood.

Gra (17): Regarding plated Kelim (Sa'if 1), the Shulchan Aruch says that we immerse it without a Berachah. There, the plating is only for beauty. Here and in Sa'if 6, the Shulchan Aruch retracted from what he wrote in the Beis Yosef.