The following advice is for US airports only.
Scissors must have a blade shorter than four inches from the pivot point.
If you’re still nervous about your best pair of scissor being confiscated, buy a thread cutter or bring a nail clippers.
Sewing needles are allowed! If you’re feeling a little hesitant, stick it into your fabric.
Magnets are allowed! So don’t leave your trusty needle minder behind.
Opt for an all plastic embroidery hoop or Q-Snap, just to make security a little easier. TSA will check stop you and check strange metal things they do not recognize.
For peace of mind for yourself and the TSA agents, keep all of your stitching supplies in one clear plastic carrier that is inside of your carry-on bag. That way, you can easily pull it out, everything will be together, and nothing should get lost.