ב
שִׁעוּר הַפְּגִימָה, כָּל שֶׁהוּא; וּבִלְבַד שֶׁתֶּאֱגֹר בָּהּ כָּל שֶׁהוּא, אֲפִלּוּ חוּט הַשַּׂעֲרָה.
Seif 2
What is the amount of defect which disqualifies a knife? Even a slight amount. As long as it accumulates even if it is a hair-size it disqualifies.