Reference for Kelim 11:4
בַּרְזֶל טָמֵא שֶׁבְּלָלוֹ עִם בַּרְזֶל טָהוֹר, אִם רֹב מִן הַטָּמֵא, טָמֵא. וְאִם רֹב מִן הַטָּהוֹר, טָהוֹר. מֶחֱצָה לְמֶחֱצָה, טָמֵא. וְכֵן מִן הַחֲלָמָא וּמִן הַגְּלָלִים. קְלוֹסְטְרָא, טְמֵאָה. וּמְצֻפָּה, טְהוֹרָה. הַפִּין, וְהַפּוּרְנָה, טְמֵאִין. וְהַקְּלוֹסְטְרָא, רַבִּי יְהוֹשֻׁעַ אוֹמֵר, שׁוֹמְטָהּ מִפֶּתַח זֶה וְתוֹלָהּ בַּחֲבֵרוֹ בְּשַׁבָּת. רַבִּי טַרְפוֹן אוֹמֵר, הֲרֵי הִיא לוֹ כְּכָל הַכֵּלִים, וּמִטַּלְטֶלֶת בֶּחָצֵר:
Ritually impure iron which was smelted together with pure iron: if the greater part was from the impure iron, [the vessel made from the mixture] is impure; if the greater part was from the pure [iron], [the vessel is] pure. If each was half, it is impure. The same law also applies to a mixture of cement and cattle dung. A door bolt is susceptible to impurity, but [one of wood] that is covered with metal is not susceptible to impurity. The clutch and the crosspiece [of a lock] are susceptible to impurity. A door-bolt: Rabbi Yehoshua says: he may remove it from one door and hang it on another on Shabbat. Rabbi Tarfon says: it is to him like all other vessels and it may be carried about in a courtyard.