Yoreh Deah Siman 18 Seif 7

ז סַכִּין שֶׁפִּיהָ חָלָק וְאֵינָהּ חַדָּה, הוֹאִיל וְאֵין בָּהּ פְּגָם שׁוֹחֲטִין בָּהּ, וְאַף עַל פִּי שֶׁהוֹלִיךְ וְהֵבִיא כָּל הַיּוֹם עַד שֶׁשְּׁחָטָהּ, שְׁחִיטָתוֹ כְּשֵׁרָה

 

Seif 7

 

When the edge of a knife is smooth  and is not sharp, one may slaughter with it, since it does not have a flaw. Even though one passes it back and forth the entire day until the slaughter [is completed], the slaughter is acceptable.