Keilim13: 3
[ג] חַרְחוּר שֶׁנִּפְגַּם — טָמֵא, עַד שֶׁיִּנָּטֵל רֻבּוֹ. נִשְׁבַּר מַקּוּפוֹ — טָהוֹר. קַרְדּוֹם שֶׁנִּטַּל עֻשְׁפּוֹ — טָמֵא מִפְּנֵי בֵית בִּקּוּעוֹ. נִטַּל בֵּית בִּקּוּעוֹ — טָמֵא מִפְּנֵי עֻשְׁפּוֹ. נִשְׁבַּר מַקּוּפוֹ — טָהוֹר.
A blade that was damaged is tamei until the majority of it is removed. [If] its socket broke, it is tahor. An ax whose broad blade was removed is tamei on account of its splitting blade. [If] its splitting blade was removed, it is tamei on account of its broad blade. [If] its socket broke, it is tahor.