I use the tiniest scissors for the trip. Mine only measure 3 inches....and I put them on a lanyard, so that I could but it in the bin with my shoes...no problem going thru.
The lanyard is also good so that you don't drop them on the plane.
Take only 1 needle with you as carryon. You can take an extra in your checked luggage. I took big scissors with in the checked luggage and needles. I put them in an outside pocket inside a pair of socks. I showed them to the person checking me in and she said that was just fine the way that I had them.