Keilim 13:8

Regarding a comb for flax, if the teeth are missing but two remain, it remains susceptible to ritual impurity; if only one tooth remains, the comb is insusceptible. Each of the removed teeth, however, is susceptible to impurity on its own. Regarding a comb for wool, if every other tooth has been removed, it is insusceptible to impurity; if three consecutive teeth remain, it is susceptible. If one of the three teeth is on the edge, the comb is insusceptible. If two teeth from the comb were modified into a pair of tweezers, they are susceptible to impurity. If even one tooth was modified for use with a lamp (i.e., adjusting the wick) or for stretching cloth, it is susceptible to ritual impurity.

Keilim 14:1

The minimum size remnant of a broken metal utensil that will remain susceptible to impurity is as follows: a pail – large enough to draw water; an urn – large enough to heat water; a kettle – large enough to hold sela coins; a cauldron – large enough to hold jugs; jugs – large enough to hold prutah coins; wine measures – large enough to measure wine; oil measures – large enough to measure oil. Rabbi Eliezer says that the size for all these is large enough to hold prutah coins. Rabbi Akiva says that a new utensil that has not yet been sealed is susceptible to ritual impurity but one that has not yet been polished is insusceptible.