Don't know if it was mentioned, didn't have time to search the entire thread, but it is my understanding that the clover type cutter (which has a small encased blade) is not allowed.
The TSA site says this under special items: Knitting Needles and Needle point:
Knitting needles are permitted in your carry-on baggage or checked baggage.
Items needed to pursue a Needlepoint project are permitted in your carry-on baggage or checked baggage with the exception of circular thread cutters or any cutter with a blade contained inside which cannot go through the checkpoint and must go in your checked baggage.